old car A/C advice

[Steve Barber <steveb@cme.nist.gov>]

I've got an '85 Audi 5000S in overall fair condition, with some A/C
problems - in particular, the compressor became *very* noisy and shortly
thereafter it apparently had lost enough pressure that the low pressure
switch now prevents it from running.  This was about a year and a half
ago, not long after I acquired it.  I have most of the records for the
car and it doesn't seem to have a history so it may have just leaked
down over time.

I've searched the archives (thanks Dan) and found very little advice
about fixing this myself.  I located a rebuilt compressor for a good
price (~$109), bought a new receiver/drier, and know that I need to
track down O-rings of the correct size at the local parts store.

I'm not really intending to switch to R-134, but... how much should I
expect to pay for flush/evacuation/R12 recharge and oil?  How about a
leak test?  And how much work is it to do the compressor swap myself?
My first impression is that the sucker is HEAVY which could make life
difficult, and access could be difficult too.

Is it reasonable to go to a shop and ask them to discharge the system,
go home and do the work, then come back at a later date?  (i.e. do they
have a way to reclaim the R12, or does it sit in the machine waiting
to be put back in the car?)

Lastly, with the new receiver/drier, any precautions necessary to keep
it from becoming contaminated in the time between installation and
evacuation/recharge?

Mainly I'm just trying to fix this as cheaply as possible. Thanks a bunch,
Steve