Installing a/c help!

It sorta is the compressor. If you try to get an old used compressor and run 134A, it will not have the right oil or o-rings in it. You should get a new reman compressor as it will already have either PAG oil or mineral oil and the proper o-rings for 134A. Mixing and matching oils old and new will cause the o-rings to be eaten away. That would suck.