[Jetjockey]

You could take off the air cleaner and hold a mirror back there to see if the top of engine has oil pooled on it. This will pin down the leak or eliminate 3 possible sources. Thermostat o-ring and oil pressure switch can be replaced with engine in car. I would personally not try the crankcase breather gasket without pulling the motor. If it is the oil cooler o-rings, I believe I heard of someone changing them without an engine drop (another thread). Rear Mail Seal would obviously require an engine drop. Of course all of these should have been changed out 8,000 miles ago with the engine rebuild. I bet it is an inexpensive fix (oil pressure switch) that the dealer should fix with a couple hours of labor.