The last time I did one a few years back, you could still get the bearings from the dealer. If not, a good bearing company should have them. Without the special puller, the races can be a pain to get out. I've seen the worm gear assy. available on E-bay from time to time in 3 different ratios. The factory service manual is the best source for rebuilding info. They're relatively easy. The most important thing is the adjustment so you don't ruin what you get replaced. It's a fairly involved process if you follow the book by the numbers but what I do with mine is first (assuming the box in out of the car and on the work bench) to loosen the top nut and back off the adjustment screw for the gear lash. Then set the worm gear bearing preload by loosening the huge steel nut and turning the huge aluminum upper bearing housing. The book wants you to tighten it so that there is between 1 1/2 to 4 1/2 inch/lbs of turning resistance in the input shaft. I find that if I just take up all the clearance by tightening the housing by hand and then hold it from turning while you tighten the nut, that it comes out just right. After you do that, double check that there is no in-and-out movement to that shaft and that it turns smoothly. Run the shaft lock to lock and check it again! Center the shaft so there is equal travel in both directions and run the gear lash adjusting screw in with your fingers until you can't turn it any more. Tighten the nut and run the input shaft from lock to lock again. Loosen the nut and tighten the adjustment screw by fingers again until you've taken up all the play. You can use a screw driver if like but don't put any torque on it. Just take up the slack. Tighten the nut and check for any binding or free play as you turn the input shaft back and forth. There should be zero lash in the straight ahead position and no binding. You'll probably feel some minor bumps in a used box but they should be minor when the adjustment in right. If the adjustment screw has to be turn in so far that the nut will barely still hold on, the gear set is too worn out and needs to be replaced.
You can do this adjustment in the car also but first disconnect the pitman arm before you set the bearing preload. Have fun!
Mark
