I used my pilot bearing puller to remove the bearing races. It looks to me like going back together is pretty straight forward. I don't remember being afraid of it. I remember thinking I could get around all the special tools. I've always used a torque wrench to check preload. There are specs listed for preloads, but the point of measurement is different. So a fish scale would likely get you close enough. Also, if you measure preload with a torque wrench before disassembly, that should get you pretty close as well. But doing it that way I think I would go back together just a smidge tighter. Be sure to check the backlash before staking everything down.
The preload of the pinion is to get the bearing clearance tight. There is tremendous side loading going on there during acceleration. It would take shims to set the depth of the ring gear. Mine didn't have any shims, so maybe they weren't required? Maybe the housing was properly machined and it was a good fit without any shims? But common sense, you'd want to peek at the ring gear depth to make sure the teeth are not bottoming out. My guess is it would be ok if going back together with the same parts. The ring and pinion are going to be a matched set, so you can't just replace one gear and not the other. But if replacing the housing, or going back together with new bearings, then that's what will change your settings. :moped:
The pinion bearing was the one I needed most, and was unable to find anywhere. And I got all the seals except the pinion seal. You won't know what bearings you might need, or not, until you get it apart.
Aside from having to get a little creative about working around special tools, the job looked straight forward to me. I've done quite a few automotive differentials and this one looked pretty simple. It ain't noth'n but some gears, and this one only has 2. I would say don't let this thing intimidate you. But you might easily be money ahead to just find a good used unit to swap out. And if all you're doing is chasing leaky seals, it may be even cheaper and easier yet.