Ditto what Steve said about the timing chain. If it is still the single row chain, at the very least feed a new one in. This is more important than any oil leak. Of course, if your friend refuses & the engine blows, let me know and I'll buy the car. The 380 is a one year only model, and I have some special (Dr. Frankenstein type) plans for one if I can find a clean one with a bad engine.
You said that the oil is dripping onto the exhaust manifold, therefore the leak is *above* the manifold. Sounds as simple as a valve cover gasket. Iíll be more than happy to change it for half of what was quoted by the rip-off mechanic. Hell, Iíll repaint the car for no additional charge as well.
$5000 goes a long way.
Make sure that what is dribbling out the back of the engine is OIL, not transmission fluid Ė the front pump seal on the transmissions are a frequent source of leaks at what appears to be the rear of the engine. In fact, it is much more likely to be the culprit.
How much mileage on the SLC?