It really isn't as hard as most people think. You just have to be REALLY careful and triple check your measurements. I'm doing mine HOPEFULLY this weekend. Going to 4.10's. For an experienced shop the rear should take about 1.5 hours, the front about 2.5-3 cause there's a lot more to disassemble. You just have to make sure that your backlash, bearing preload, and pattern are correct. It just takes patience and time. And there are some tricks that save you a lot of time. The biggest one is that you measure the thickness of the new pinion and the old pinion. The difference in the gear thickness is how much shim you have to add or subtract from the shim pack that was originally in it. This will get you very close the first time. Also, get an extra inner pinion bearing and have 0.0015" honed out of the center. This will make it a slip fit instead of a press. This lets you slip the bearing on and off to adjust pinion shim until you get it right, then you press on a new bearing and put it together for final assembly.

The first gears I set up were in my Blazer. The front is WAY out. They were actually bound when I put them together but I didn't have the tools or time to get it right, I had to run it. Made a little noise the first couple times I had it in 4wd, but then quieted down. It was my daily driver for a year after that, and it's been a wheeling rig ever since. Those gears are still going. Worn pretty bad, but still going.