1993 Chevy Suburban How bad is it?

My Suburban has been slowly showing some mechanical issues. In the last month I've noticed that my oil pressure has been slowly going toward the, "NO PRESSURE, " area. Until recently the service engine light had not been on. The other day after I got on the freeway, the afore mentioned service light came on but the car seemed to be running fine. When I got off the freeway the truck started running kind-of choppy and the oil pressure went all the way down below zero. At that time, I went to pull over and the engine sounded okay until it got near the top end of the rpm's before it shifted. The sound that came from the engine was loud and sounded like it was a deisel engine. I have only driven the truck a couple of times since and it seems to be getting worse (louder), BUT, it only does this when it gets warm. The only code the computer has given me is #32, (egr system problem) but it sounds worse than replacing an egr valve. Any suggestions?