02 Dodge Ram 1500 4.7L 4x4 oil pressure problem?

[dodge boy]

I don't drive this truck much anymore, but it's got about 108000 miles and I have put less than 2000 miles on it in the last 3 years. I was driving the other day, and was stopped at a stop sign. The check gauges light came on and the oil pressure dropped to 0. I heard no noise from the engine, and everything seemed fine. If I hit the accelerator, the oil pressure went back up and everything was fine. But, when I stopped again, it was the same deal. Just wondering if it would be the pump, gauge, or sensor/sending unit. Also, my blower motor makes a horrible noise. Does anybody know how hard it is to change these out? Thanks