Remove the 2 screws at the front of the shifter cover
Slide it back so the rear end clears the metal lug that goes in the hole at the rear of the cover.
Slide it up the shifter stalk and put a clothespin od spring clip on the shaft tp keep it out of the way
Look on right side of shifter for a grey triangular shaped thing. Notice it is secured with 2 screws, loosen them, turn the key to II pos and then move the box rearward just a tad. See if rev lights stay on when you move shifter back and forth. If ok then put back in park and tighten up the screws.

Sounds like low freon in system. See if jumping it like rhaire said makes compressor come on then before you do a DIY freon job check all the pipes for OBVIOUS leaks/breaks (at the compressor if the rubber isolator bushings get sloppy the compressor can shift and contact one of the metal pipes that carry freon to evaporator or condenser. Try moving the compressor, if it moves then most likely the pipe is worn or cracked. Its an easy junkyard pipe to find but swap rubber busings as well then get a pro to properly evac the system and do a dye test for leaks before fill up with freon-if not already R134A then now is the time...