Ok, I have some updates to anyone who may be interested or encounter a similar problem. (To answer your question above, the oil pan has never been replaced on the car).....
I brought the car to the dealership a few weeks ago to have the front diff looked at.
According to the tech notes and service advisor, the bottom bolts on the differential hosuing were "loose", i.e. not torqued to factory spec.
Clean up the entire area and retighten bolts. Bring back in a week or two after driving around to re-inspect. The first attached pic is right after I got it back, made me realize just how grimy it was before.
So I put about 300 miles on the car in the next 2 weeks, and check under the car and sure enough, new oil covering the bottom of the housing (See the 2nd pic I took). I didn't really expect just torquing those bolts down to fix
whatever the problem was, nor was there any reason for those bolts to need tightening in the first place. So back it went to the dealership yesterday.
Well, I got a call that the Service Mgr. gave the go-ahead to order a completely new front differential unit
. I was actually surprised it wasn't just a pinched o-ring or shaft seal that they would try and replace.
Based on the cost of that unit, as well as the labor involved, all I can say is...