Pay someone and see if they will let you watch. Gears require very good setup or you will have problems down the road... Just check out Ambo's thread about this
The big deal is the specialized tools that you need. Since you probably won't be doing this a lot, just pay the $200 and let someone else do it. that's probably cheaper than buying the necessary tools.
To do it properly, you will need a dial indicator at the least. It is best to have a press to press the ring gear and pinion bearing, but it can be done with a hammer and a brass drift for the ring gear and driving the pinion bearing onto the pinion with a proper sized length of pipe. NOTE that I am not reccommending this, but this method is not totally uncommon.
You can get a pretty good video out of the Summit racing catalog. This video is put out by Richmond gear and is only about $15 or so.
There are alot of people that really discourage putting in your own gears. I researched it for about a month and got a good grip on all the components and theory behind backlash and setting up the ring and pinion and decided to buy the dial indicator and have at it myself. I found it quite easy. Just a little time consuming. The FRPP gears went into my 2003 GT Vert with very little shimming. Another great tip is using hot and cold to your advantage to fit the parts. For example instead of having to press on the bearing, or pound it on using pipe. I put the pinion in the freezer overnight and boiled the bearing and it dropped right onto the pinion. Same priciple for the ring on to the differential. I'm not saying everyone could do it. There is some precise measuring and math involved. I eventually found 2 very good write-ups in the web that I used to walk through the project. I might be able to find them again if you need them. Also the one other tool I had a hard time finding was a Inch-Pound beam style torque wrench. This tool is needed to set the preload or tension on the pinion gear.
If you check the pattern on your gears once its installed there is a guide that tells you what the pattern should look like and if its wrong what you need to adjust. All in all I was glad I did the project myself and not only learned alot but saved a few bucks on the install. Peace.
I would respectfully disagree, in order to install new gears, you will need one of these, or you could pull the pinion in and out about a hundred times to get the right gear pattern. the problem is locating the center of the ring gear. You must use a tool that fits in the bearing saddles, then measure from that to the end of the pinion (you could add or subtract shims based on the stock pinion depth and get close) You take that piece, divide it by 2 (to get the center) and then either add or subtract shims to reach the depth that is stamped on the head of the pinion. Setting the backlash is no big deal, a dial indicator works just fine for that. It's the pinion depth that screws you, and without it correct, the contact pattern will be off, and the gears will most likely whine and have a shorter life.
This is the tool you need: http://www.completeoffroad.com/wsm/i-63_pinion_depth_tool.html
the heating/cooling of the bearing is a great idea, but if you have to set the pinion depth, (and being new at this you will have to take a few shots at it) you must remove one of the pinion bearings, for this reason they make "set up" bearings that are easily removed.
A pinion depth gauge is very handy, but is not necessary and not a justifiable expense for a hobbyist who will do this work only a few times in their lifetime.
To begin with, you should PLAN ON using FRPP gears because in most cases they go in perfectly by just using the shim sizes from your current setup. Put the pinion bearing on the new pinion using the same size shim as your current one. If that does not set up your pinion depth right on the money, it will be very close.
Then put pinion and carrier in place, again using the same shim sizes that were used on the carrier bearings. Once that is in place with the pinion bearing tight, but not necessarily preloaded, and without the crush sleeve, check the backlash with the dial indicator. If the backlash is correct, then put white grease or pattern compound on a section of the ring gear and run the pattern. If the pattern is correct, then you are there. If not, consult most any car repair manual to see which direction to move things around in order to get a good pattern and adjust shim sizes accordingly.
Once the setup is correct, you can now use the crush sleeve on the pinion nut and tighten for correct preload. Yes, if you haven't done very many, you should find a beam or dial in/lb. torque wrench for setting the preload.
As far as the controversy regarding whether or not to do it yourself, we here on a forum CAN NOT advise you. It depends on you! If you are a studious and determined person who has turned bolts some in the past, then don't let anyone discourage you. If you are not, then find a reliable shop. There are always those naysayers who are not determined enough, or are uncomfortable with such an operation themselves. When that type of person makes a recommendation, they are making that based on THEIR OWN comfort level with such a project. If you feel that you are up to it and are willing to do the necessary study, take the proper care and spend the needed time, then I say GO FOR IT!
Just another tip for those interested. Instead of buying the "set up" bearings. When I pulled the old bearing off of the old pinion, I ground down the inside of it so it fell right onto the new pinion. This way I used it to set up the pinion depth with the loose one then once I established what shims I was using I put the new " tight" bearing on the new pinion. It saved buying the set-up tool that I would probably only use once.
bwhipple makes a good point, I've done the same thing, I never really understood the idea of "set up" bearings when you have a perfectly good set of "old" bearings that could be modded and save $$$$.
Here's a start on the tech article http://reiderracing.com/rtech.htm http://www.moserengineering.com/Pages/axletech.html http://www.thedirtforum.com/differential.htm
This last article is what you have to do when you don't have the pinion depth tool (which you don't). It's actually a pretty good article, but I'm a pinion-deoth tool guy and alway will be