I’ve seen a number of very detailed articles and videos on how to do it. To some degree or another I understand it as well, especially after having had to set the gear lash so many times on a number of 1/5 scale RC cars I’ve owned.
Part of me thinks it’s something I’m building up in my head to be much harder than it actually is.
I have actually done gears myself in every case. I did all of my full size blazer gears, and all of my jeep gears myself. I have done a number of Toyotas which are like miniature Ford 9 inchers. Those are pretty easy in reality.
For the most part if you take it apart and put it back together using the same shims to get you started you are going to be pretty close. Or that is the case for me. I usually re-use the oil slinger behind the pinion bearing if at all possible. In every gear change I have done, I have not had one fail ever. And on one of my blazers I had would change rear carriers with a welded carrier and mismatch the ring gear. It was never noisy nor ever blew up. I think people are afraid of it, for the most part, but I think they are pretty forgiving too. Not to say that you can't screw it up, but I think the first time you do it you are so meticulous you will get it pretty close to perfect.
For me if you get the pattern right, and the torques right they will last a long time. The hardest part for me is crushing or not over crushing the crush sleeve. Especially if you are doing this at home, without a good air compressor. It is really hard to get the crush sleeve to start the crush but once it starts it is nothing to over crush it. I get it to start to crush then measure the turning diameter with an inch pound torque wrench. If it is too tight, I start over with a new crush sleeve. That I think is the most important thing to get right, because if it is too tight the pinion bearings will wear out prematurely or get hot and smoke the fluid. And checking the pattern when you are done. You want the pinion depth right and the ring gear in the pinion right.
I saw a youtube video where a guy crushed a crush sleeve with some channel locks, a socket on a breaker bar, and a floor jack. I think I am going to use that technique the next time. it seems like it will be strong enough and slow enough to get it the first time.
For me I don't have a press, I usually cut off the old bearings with a die grinder, and pound the new ones on with race drivers and sockets. But the most important tool would be a inch pound torque wrench for measuring the turning torque of the pinion.
I am sure people will argue with me, and tell me that it is super important for it to be critically put together, but I have done a ton of these, and some of them I threw together to get back on the road, most I have done on my back in the garage, and none have ever left me stranded. I can only tell you about my experiences though.
I will tell you if you do it yourself, and it works, there is nothing like the sense of accomplishment.
This assumes you are mechanically inclined. if you don't understand how a differential works, I wouldn't suggest doing it yourself, but if you normally work on your rig yourself, I do think this is something a back yard mechanic can do or figure out. Especially as someone mentioned before with all of the videos out there.