Having Trouble diagnosing Slow Oil Leak

[NDtruck]

heya all, I've got a '96 legacy wagon with 2.2L. I've had the the vehicle for a few months now and it's always looked like there is a slow leak somewhere on the engine as the underside of both heads are pretty oily looking. Also on the last oil change I noticed a minor oil drop that looked like it was begining to form on on one of the exhaust bolts...so I'm thinking ultimately any oil is falling from there.

I'm going to pick up some simple green soon and wash the engine as best I can so I can hopefully see better where the leak may be coming from, but my question is this: Are there any distinguishing features that I should look for to better differentiate between leaks from valve covers, heads, cam seals, or rear main? For example, if a rear main seal was leaking would the oil travel to the undersides of the heads or lower front of the engine?

In general the underside of both heads as well as the rear of the engine down to the oil pan right now are pretty oily. Likewise I'm starting to detect a faint burnt oil coming in the cabin thru the vents as well as in the engine bay after the engine is good and warm.

[Manarius]

I bet it's valve cover gaskets myself. That's one of the most common leaks I know of.

[NDtruck]

I'm hoping for valve covers too. the engine just crested 200k so it's due...