I have a 2001 Monte Carlo ss with the 3.8 and it has been leaking oil for awhile now.the oil is all over the oil pan and dripping from the bolt heads.Could this be a rear main?I can't tell if the oil is coming from the pan or higher above.The engine has 189,000 on it.

Yes, it could be. Try cleaning everything with brake cleaner, being sure to keep it away from oxygen sensors, and watch it closely to identify the source of the leak.