remove the access panel. it's held on by either 13mm or 10mm bolts (depending on when it was made) this will expose the transfer gears. if your car has the locking retainers on it, remove them they're simply 2 13mm bolts. now, take a 32mm socket, and a long breaker bar (and a pipe too, i needed one, my impact gun works great here). break both locking nuts. (once they're free you can spin them with your hands) now take a standard power steering wheel puller, and put it over the gear (top/input shaft first, and make sure transmission is in Park, or the gears will just spin) then just pull the gear off.

you now have two options when installing the gears:

1) you need to modify the case. you'll need a dremel (or die grinder) to remove material on the case, to allow the output (larger) transfer gear to fit on. (see pic) make sure that no metal shavings go into the case. you're removing aluminum, and aluminum isn't magnetic so the pan magnet won't collect the particles and they'll eat up your transmission.

2) the lower output gear bearing can be shimed. you need to shim the bearing so it site 0.26" away from the face. Picture #1 Picture #2 . doing that will cause it to not rub on the case.

to install the new gears, simply position the gears over the shaft, and push down. then take the locknut and use it to push the gear down all the way. tighen the locknut to 200ft/lbs, and reinstall the retainers. remember to put a new RTV seal around the plate.

now about shimming the gears. if you have a Dial indicator, you can check to see if the endplay is set. it should be between .05mm and .25mm (.002 and .010"). if you don't, use a inch-pound torque wrench. if the torque required to turn the gear is between 3 - 8 inch pounds, then the shimming is correct.