I can wrench but I'm definitely not an expert myself. Swapping in a used 3rd member is pretty simple as you're just unbolting the driveshaft and then removing a bump of bolts on the diff to slide it out, but beyond that I'm paying someone to do it right. Not trying to sell you on that option though... if you don't care about highway mileage and you don't plan to pull a heavy trailer then I'd go 4.88 in a heartbeat if you're bothering to do the regear at all
If you can find someone selling the fully assembled 3rd member for the rear and the entire clamshell (basically the whole diff) for the front, probably any decent mechanic could do it for you in a day. When you're done sell the old 3rd member and old clamshell to recoup some of the cost.
That said I went with Nitro gears in part because I had 110k on the truck and plan to keep it and I figured new Nitro gears set up right will likely last as long as used OEM gears. Also I didn't have to risk receiving a used 3rd member or clamshell that is actually in bad (or just marginal) shape... something I wouldn't know until I had swapped everything over. If I had 300k on the truck and needed a set of gears I would've looked in the salvage yards.