Hi there. Just wondering, when you replace an ac compressor do you have to remove all the gas. The A/C is the old R12 so would involve cnversion to the R134a. I think the bearings or bushings in the AC are on the way out. Can see the wheel on AC wobbling a bit when A/c cuts in and noise as clutch cuts in and out. The AC is cold enough so wondering when it dies could I just get compressor from wrecker or something without replacing gas?? Thanks