+1. I've been wrenching for about 14 years, and I still don't touch gears (not because I don't have the tools, but because I'm scared). You need (yes, some can do without) a press that can remove some of the bearings, and you dial dial calipers that can measure 0.001" with accuracy. Plan on it taking a full day if it's your first time, and you will be putting the parts in, measuring, taking them out, measuring, adding shims, and repeating that process over and over until it's perfect. Yes, perfect. "Close enough" will leave you stranded after 200 miles. If the wear pattern isnt spot on, and if you dont give your gears the proper heating/cooling cycling immediately afterwards, you will end up with a grenaded rear end.
I pay a local mechanic $80-100 to do it. Totally worth it.
I have 35" tires on my 31 spline 8.8 and I run 4.88 gears. It's a great combo, and these gears are great for this size.
If you are cruising the highway mainly, then maybe 4.56 is a good idea. I cruise 70 mph at 3000 RPM. Gas mileage would be better if it was more around 2600 RPM. I do mainly city driving and dirt playing, and 4.88 is great with my 4.0L and 5 speed.