PACIFICMAN

I have a 2001 C240, 2.6 V6, Auto Trans. 70,000 miles. Lightly used but well maintained by previous owner. I just performed an oil change after 10,000 miles. When I removed the rear bottom cover it had oil residue in it, a fair amount. However the transmission was covered in oil, not ATF. There was essentially NO oil forward of the Trans / bell housing. There was no appreciable loss of oil from the crankcase(I drained 8Qt out).
I presume this is the rear seal failing. Is this a known weakness? Has anyone been down this road? I am curious if this is a drop the drives shaft, ease back the Trans, replace the seal job or a full engine pull?
Thanks in advance!