I recharged it one night and it was out again by the next morning, so apparently I have a leak.  Where is the most probable location in the system for a leak and how difficult will it be to narrow down and fix?

Thanks.

Wal Mart sells injection kits for leak detection with UV Dye in them that will fluoresce under a UV lamp.

hmmm, does Walmart sell UV lamps too?  Would a blacklight work?

Was it working before you charged it ? It is possible to put too much freon and overload the system. It should have a high and low pressure cut off switch.  .

Look for oil stains at the condensor, rec/drier, compressor fittings into the fire wall. IF it is a leak it should have an oil stain were its coming out if its leaking down that fast.

Last GM leak I fixed was at the compressor shaft seal.  

If you repair the system it will need to be drawn down to a Vaccum BEFORE any new freon is installed after the repair. If not the system will not charge correctly.

Quoted: hmmm, does Walmart sell UV lamps too?  Would a blacklight work?

The last time I was in walmart they had a whole shelf full of dyes and kits. Most black lights are too big but would work IF you can get in into the small space the seals live. ..

It may be very well that the 0-ring in the A/C may have rotted out or gone bad, same happened on my mom's 2000 Blazer.  

I had a similar problem with the wifes Diamante.  Charged it, sealed it, still no worky.  It ended up being the evaporator being all clogged up.  Had to take the dash off, remove evap., blow it out, and reinstall.  Now the A/C is freezing cold, like new.