2007 Pontiac Vibe Engine oil light

The warning light refers to oil pressure, which is critical, not level. It's common for the pressure sending unit to fail, but given the mileage, and especially the sounds of serious engine damage, the pressure most likely really is low due to worn engine bearings. Your mechanic can perform a pressure test with a mechanical gauge to verify it really is low, but the bottom of the engine will need to be disassembled to do a thorough inspection.