Oil Pressure Sensor

We have an 87 Cutlass Ciera which was recently hit in the passenger-side door. When I started to drive it to the body shop, I noticed the oil pressure gauge only registers about 12 PSI. I find no oil leaks and the engine is full of oil. I haven't been able to find the oil pressure sensor on this thing (help); the wire may just be knocked off. Also, the car was struck on the right side just next to the "black box". I'm wondering if that could have been knocked out of wack. I want to be sure it's the gauge and not the actual oil pressure that's the problem, before I attempt to drive it to the body shop.

Oh, BTW, it's a four-cylinder engine.