Oil burning in 2002 model

[rmf1986@sbcglob]

Hi All,
My 2002 seems to have a slight oil leak, as witnessed by a small drop on my garage floor, and worse, the smell of oil burning as it apparently hits the hot exhaust manifold. I cannot seem to pinpoint the leak from the top or bottom of the engine, but is it most likely a valve cover gasket, or head gasket?
I do not get a coolant smell, so it seems like the head gaskets are OK.
How much of a bill am I probably looking at to repair?

Any insight would be great!

Thanks,
Ross