5.38 Swap

Either 3.55's or 3.73's will be fine.

Setting up gears is not all that difficult... if you have done it a few times. If you haven't it can be tough. If you make a mistake setting pinion depth and backlash those $200 gears will turn to junk real fast or be very noisy at the least. Don't forget the installation kit which includes bearings, pinion seal, and shims to install your new gears.These kits generally run approximately $125-$135. Also depending on which yoke you have you may need a new one of them with a different spline count also.
Unless you have the correct tools which include a hydraulic press for the pinion bearing, an inch/lb torque wrench, a ft/lb torque wrench and some precision measuring tools to set pinion depth and backlash you may have to pay to have them set up which can run anywhere from $100 on up depending on the shop.

A used pumpkin for almost $500 doesn't sound like such a bad deal anymore.

The good thing about buying new gears and bearings and having them professionally installed is they will be all new. With no worries. A used pumpkin may need new bearings and pinion seal or they may be perfectly fine.