A/C only blows warm air although the engine changes idle speed when the a/c is turned on so I'm assuming the compressor is trying to work.

After the a/c ran for 10 min both lines leading from the compressor were warm.

Next step I suppose would be to check a/c system pressurization. My experience with a/c systems losing pressure in the past resulted in a slow loss of cool air where it gets less and less cool until the air finally isn't cool at all...which coincides with the 'freon' slowly leaking out. Since this happened all at once should I assume there's a major leak somewhere and should do some kind of system pressurization test before I dump more freon in? Or should I be looking somewhere else in addition to checking freon?