R12 changed over to 134A

I need to change out the AC compressor on my truck, the old system was R12 but when I had an accident with the truck it was changed over to 134A. My question is when getting a new compressor most say for R12 systems and I know they come with oil in them, maybe not all of the oil but you put in what you need if necessary. So is this going to be a problem when I go to recharge the system with 134A or does the oil has to get drained and flushed out on the new one? The compressor didn't fail so there shouldn't be any reason on flushing the system I wouldn't think, right? It was leaking around the compressor it's self so I just unplugged the wire going to it and taped it off until I could get to it. Also in replacing the compressor some suggests on replacing the accumulator and orifice tube I would like to get your input on that as well. I appreciate any input. Thanks, Jason