This is the quickie way we do it here at the shop. It is quick and dirty, not for the timid. Please have a look at http://www.vfaq.com and make sure you understand the ramifications of screwing up. If you screw up, you will have a rough running motor at best (one tooth off) or 16 bent valves at worst.
Remove the upper timing cover.
1G Cars: Remove the upper motor mount and
remove the upper timing cover bolts so
that the upper timing cover is loose and can be
pried back some.
On 2G cars: Remove the motor mount.
Remove the two motor mount studs sticking up
vertically. Double up 2 nuts and lock them against
each other. Unscrew the lower nut to
remove the stud. Remove the mid timing belt
cover.
Rotate the motor until the number one cylinder is at Top Dead Center. Only rotate the motor clockwise, you risk the timing belt skipping a tooth if you turn the motor counter clockwise. Don't risk it. The crank pulley nut has a 1/2" square drive hole in the end of it. You can insert an extension through the access hole in the plastic splash shield in the inner fender. The easiest way to turn the motor is to put the car in 3rd gear and roll the car forward until the timing marks line up. This will be when the pins in the cam gears are both pointing up at 12:00. Use a flashlight and make sure the timing mark on the crank pulley lines up with the "T" mark on the timing cover. There are notches on the timing gears, you will only be looking at the two marks where the pulleys are together in the center. By using a straight edge, make sure the marks are dead center through the center line of the cam bolts. Do not trust your eyes to be sure that the marks line up through the center of the bolts, use a straight edge. If this does not all line up, stop here. It will explain the rough idle and low vacuum you had and give you a good reason not to have that same guy do your timing belt again. You will need to completely re-do your timing belt set up and tension. DO NOT use these instructions.
Remove the valve cover. Remove ALL the 10mm head bolts on the cover. If you miss one, you will break the cover when you are prying on it trying to get it unstuck. There are around the out side and in the middle section. One sneaky one is tucked in by the water pump pulley.
Break loose the 17mm cam gear bolts. They can be very tight. You will end up using a large adjustable wrench on the cam to hold it and a 17mm socket on a breaker bar on the nut. Often a large pipe needs to be put on the adjustable wrench to get more leverage. There are times when you swear you will snap the cam they are so tight. Have not snapped one yet but when they finally break loose...makes quite a noise. For now, just break the nuts loose, do not remove them.
2G cars: Place a board under the oil pan and
raise the motor slightly with a floor jack. This
allows you to get a socket on the intake (rear)
cam gear bolt.
Use some plastic zip ties to tie the timing belt to the cam gears. Use at least two ties on each gear.
Pull the access plug out of the rear part of the timing cover. It has a little tab on it that you can grab. Insert the cam tensioner tool through the hole. Further inside the hole the tool will thread into a hole. Keep turning until you feel some resistance. This is the tool beginning to depress the tensioner. Turn slowly. If you turn too fast, the tensioner can not depress fast enough. When it gets tight, wait a little and try again. If it is still tight after waiting a little, you are done. The belt should be loose now. Grab it at the top between the gears and it should have some slack.
Start with the exhaust cam. Remove the cam bearing caps. Notice that they are stamped and numbered. There are arrows pointing in the same direction. You will be installing them in the exact same location and pointing in the correct direction. After removing the bolts, the caps can be stuck on. You can put a large Phillips screw driver or similar sized tool inside the bolt hole of the cap. Gently rock the cap front to back till it comes loose. Put the caps somewhere safe and lined up in the order they came off.
Remove the bolt for the cam gear. Pull the cam gear off the end of the cam, just pull it off slightly so that is rests next to the cam and does not drop down or fall to the side. Keep the belt at least partially snug. At this point, do not let the motor turn over. Keep the car in gear and the parking brake on.
Slide the exhaust cam up and out. Remove the cam seal. If your car is newer, you can most likely re use the seal. If you have some mileage on the car or are more cautious, now is the time to replace it. The part number is MD133317
Install the new cam. Use some assembly lube on the bearing journals. If no assembly lube is available, motor oil will do. Make sure that all the rocker arms are in place and sitting properly as you install the cam.
When installing the cam bearing caps, be sure that they are in the proper order and direction. When installing the two caps at the cam gears, a little swipe of silicone sealant needs to be applied to the cap. Just a little, you don't want any squeezing into the bearing journal. Torque the cam cap bolts to 14 lbs.
Re install the cam gear. Pull the gear up and the belt taught. If your belt is still tight, you may need to _Slightly_ turn the cam so that the pin in the end of the cam lines up with the holes in the gear. Either way, get the pin in the hole first, then swivel the gear and/or the cam to get the bolt hole to line up. When the gears were removed, the cams naturally rotated a little. You will be just countering this. Once the gear is on, start the bolt, don't torque it yet.
Next is the intake cam. Before removing the cam, you need to remove the cam angle sensor (except 95-96 cars).
1G cars: Remove the cam angle sensor. Mark the
location of it's adjustment. Note the positioning
of the tang that goes into the cam. There is a
little dot and a notch that should line up. They line up
when the motor is at #1 TDC.
2G 95-96 cars: The cam angle sensor is
underneath the intake cam gear. The cam gear can move
out but if you force it up or down you can break
the plastic body. Be careful.
2G 97-99 cars: The cam angle sensor is back on
the end of the intake cam. Remove the 3 bolts
holding on the cap. There is a 12mm head bolt
holding the sensor trigger. The trigger must be
removed before the sensor body can be removed.
Note the orientation of the trigger cylinder.
it has a long gap and a short gap. You need to get
it back on the same way.
Time to torque the cam gear bolts. Remove one bolt and with the cam gear staying in place, put a little blue Locktite on the threads. Hold the cam with the adjustable wrench holding the cam. Take care to be sure that the cam does not turn.
Remove the tensioner tool, replace the plug.
Now may be a good time to replace the valve cover gasket. The main gasket is part number MD125939. There are 4 separate gaskets at the spark plug holes, you need 4 of MD125940. The little 1/2 moon piece is part number MD050536. Either way, put just a little silicone sealant at the corners of the caps that are right at the cam gears and a little at the 1/2 moon piece. Notice that the long bolts go around the outside, the shorter bolts go towards the inside. When tightening the valve cover bolts, do them slowly and evenly. If you tighten one too much, you will crack the cover. Tighten them in a circle pattern a little at a time. The torque is only inch pounds. This is just snug with two fingers on a 1/4" ratchet.
Replace the timing belt covers and reinstall the motor
mount.
Let the car sit for 3 hours minimum. When you removed the cams, the
lifters were allowed to extend fully. They will naturally bleed back
down. They just need a little time. When ready to start the car,
crank it over for oil pressure first. Remove the ECU fuse so that the
motor will not start.
1G cars: Remove the MPI fuse at the battery positive terminal.
2G cars: Remove the motor fuse in the fuse box under the hood. It is the center blue fuse in the top row
Before turning over the motor:
Did you torque the cam gear bolts?
Did you remove the tensioner tool?
Did you remove any extensions or ratchet from the
crank pulley?
Crank the motor over until you see the oil pressure light turn off. Crank for an additional 10 seconds. Re install the fuse and start the motor.