send a oil sample off to a lab (phenix labs, proxis, ect) cost about 20$, takes a week and you'll get a nice and professional report to throw in the dealerships face.

Keep in mind oil pressure tends to be greater then coolant pressure so for a leak to be coolant to oil it's either really bad or only happening when the car is shut down.

The biggest problem with head gasket swaps is most of the time the head (or possibly block) will get warped from the over heating. The head or block need to be decked in order to fix the problem. Especially with an aluminum block/head.

If I recall that engine is a open deck aluminum block, so chances are the bridges between the sleeves are cracked/warped. Over heating, beating the **** out of it on test drives, pretty much any hard abuse can tax them and thats usually the weakest link on a open deck/sleeved block.

crap on the underside of the oil filler cap is the old tried and true method, a mechanic telling you "it's probably condensate" shouldnt be your mechanic. show him the oil cap to your other car and it's lack of crap under it.