No oil pressure

I have a 1995 dodge 1500 with a 5.9 v8 mageman, it has 111,626 miles on it. Its two wheel drive, with an automatic trans. It runs great, starts up and drive with noting wrong, I just change the gear fluid in the axle and transmission fliter and fluid also. I was leaving for work one morning and I heard this pop, then I had no oil pressure at all, but it still runs fine with no problems at all. I have a small oil leaks, that seams to be coming from between the trans and engine. I ask the guys at auto zone and they told me it was the oil pressure sensor, that is on the driver side near the front of the engine, I can't find it. Does anyone else have any clue to why its leaking oil?