It might have a small leak and just need a charge, it might be a bad A/C compressor, or the compressor clutch or even the ignition switch.
It's been my experience that adding refrigerant to a leaky system is just a waste of money. Find out what's failed and decide whether it's worth fixing.
Lots of threads on this subject if you use the Search tool.
Like this one:http://www.grandprixforums.net/air-c...sue-33087.html
FWIW, when mine quit, it was a bad ignition switch.
Blower speeds, DIC, DRL and sunroof were also affected.
If the ONLY thing wrong is the A/C is not cold, it's probably not the ignition switch.