My '90 Westy was converted 4 years ago to 134a by a shop in Denver just
before I bought it.  Have the sticker on the airbox and everything.  At
the time, it blew cold (enough) air on my neck for my needs here in the
PacNW.  At some point at least a year ago, the AC stopped being cold.
After major whining from my wife and kids on recent hot weather trips,
it's time to get the cold air back.

Dropped the van off at my VW shop and they diagnosed no refrigerant and
a slow leak through the AC shaft.  Sounds normal based on what I have
read here on the board.  Quoted cost for new compressor is over $600
plus several hundred in labor, so close to a grand when all done.  The
shop said that with that leak, a charge would last maybe 5-6 weeks.
Considering our limited summer, that doesn't sound too bad to me since I
really just need to get through a long trip through california at the
end of July and some hot days here and there.

Based on this I am considering:

1.  Buying a new compressor from another vendor and installing myself.
If so, what is the procedure since I already have a converted system.
Other parts to buy etc?  Best sources?
2.  Just charging it and seeing how long it will hold up.  What is the
correct/best procedure I can do at home?  What tools gauges do I need?
Does the speed of the leak correlate with usage at all?  Would any type
of sealer help slow the leak?

I have some pretty solid mechanical skills but very limited experience
with AC.