My AC recently began to work only intermitently, then not at all. I took it to a shop who did a tracer dye test and found a leak that was fixed with a $5 shrader (sp?) valve, then they added 1 pound of r134.

AC worked for 1 day or so, now it's bad again. Seems like the compressor doesn't even turn on despite fooling with all of the dash switches. Do I have a bad compressor? How do I troubleshoot? thanks.

Take it to another shop or dealer who knows you car as "adding a pound" without first knowing how much freon was in there (assuming here?) is foolish.
One should recover and evacuate the system, then add the correct charge of 1.65 lbs as too much freon is just as bad as too little (poor cooling).
The shroeder valves on those don't typically leak either so I believe that someone has misdiagnosed the real problem. If AC dye wasn't installed, it should be as that's how Volvo and most other find leaks these days.