Does the oil pressure switch (near the oil filter) leak oil? If so it's bad and needs replacement. Whether you replace it or not, but the light continues to come on and there isn't an obvious reason like damaged wiring, remove the pressure switch and attach a test oil pressure gauge. If you don't have one, your mechanic definitely should.
Do this ASAP, probably should get the car towed, not driven with the oil light on, too much risk to the engine.
If you want to find a GM specialist, here's a directory link for you: