These trucks don't usually mind sitting depending on how dry your climate is, when I drag home projects it can be 1-3 years before they come into the shop
You can pretty much plan on doing a fuel pump/ filter but the PCM and such usually hold up really well
I keep cats around to keep the mice away, unhook the battery, support them on blocks if I plan to save the tires, fill the fuel tank (less varnishing possible) and put a box of baking powder in the interior to suck up moisture. Then cover them or set them in the shade and work like heck to get them in the shop asap
I have had a few bad PCM's over the years. Usually some sort of voltage spike or moisture intrusion can lead to their demise. The 91-94 trucks are getting older and we have had to buy aftermarket/ reprogrammed pcm online a few times here and there. Those can be a crapshoot. Maybe 5 or 6 bad pcm in 20+ years of working on these trucks...they are pretty dang reliable!