i have a 91 camaro v6, my ac compressor was cracked so im takin a risk and bought one from a junk yard. still had pressure when i cracked the lines so good sign there, but the compressor i pulled from my car has a electrical connection on the back and the one i pulled from the junk yard does not. just a plug kinda thing, do i need to swap it and if so how do i do that? or can it work without it

 

That's the high pressure cut out switch. To remove the one from your old compressor, you'll need a snap ring tool. (Need to look closely to see it)

The junkyard one I'm assuming should be the same way.

 

Needle nose pliers work on that ring as well, although it's not as graceful a removal - mine almost flew away when it popped out - but it works.