I would go to the junkyard and pull one. If it breaks, you know not to do that again, pull another.
Rebuild the one you bring home from the junkyard (87-96 XJs use one iirc, might be 91-96. 97-01 use a different one, but they can be adapted to work either way if you want to cut&splice some wiring) then remove yours and replace it with the junkyard rebuilt one. Now rebuild yours. You now have a spare and enough practice to do this again when it comes time...
Remember that "shorting out" and "grounding out" are the generic "something done broke" terms for electrically-ignorant folk. They actually do have a meaning but they are misused constantly and in ever changing ways. Since your reverse lights don't work, my bet is that it's actually got a dirty contact that isn't closing at all, nevermind "shorting out." Also, the NSS has absolutely nothing to do with the AC compressor fuse and he either should not be trusted to work on car electronics at all, or is blowing smoke up your ass and shouldn't be trusted to work on cars at all.