I bought a 1998 Cadillac Catera with 77000 miles on it yesterday at an auction. While driving it home it began to over heat. I got home and popped the hood and the engine is covered with oil. I checked the oil level and it's good. I let it cool down for abour 3 hours and start it again and the oil pressure gauge is more then 3/4's of the way up. almost pegged. It then comes down after it warms up and after about 5 or 10 minutes the oil light comes on. It's the warning with the oil can and the squiggly line under it. Does this sound like an oil sending unit bad? I live in a rural area and I don't want to drive this to town to have a ODB meter put on it due to the fact that the car will probably overheat again. Does Autozone lone those out? Any,advice is appreciated, thanks.

Rick