1992 Buick Century AC not blowing cool

I recently had the compressor replaced on my 1992 Buick
Century. I had it replaced because it broke after having
freon put in it because the air wasn't blowing cool. I
think the guy might have put the wrong kind in or
something. All I know is that shortly after he put the
freon in there was smoke coming from the compressor and
there was round piece of metal that disconnected from the
compressor. So I recently got another compressor installed
by a different guy. He used one of those converter kits to
convert it to the r134a freon. He but the neon green oil in
before adding the freon and used a gauge to decide how much
freon he needed to add. He used (2)12oz. Cans of freon with
stop leak included and (2) 12oz cans of pure freon before
he got a gauge reading that he was satisfied with. I had
cold air for about 20mins and he told me not to turn the
air off so that the freon could get to circulating good.
After I left I went to the gas station and I just turned
off the engine to get gas, when I started the car back up
the air was no longer cold. I took the car back to the
mechanic so that he could check for leaks. He said that
there where no leaks because the neon oil would tell where,
but he said that most likely I need to have the condenser
and accumulator replaced. I want a second opinion, does
this sound right to you? How can you tell if the condenser,
accumulator, or any other a/c related part is bad? I need
air in my car I live in Memphis and it gets way too hot.
Thanks in advance.