My original 95 SL2 needs new oil seals as it has soaked a perfectly good clutch which has been slipping off and on for the past 2 years. I've got the transmission/bell housing removed which involved removing the entire front underpinnings and engine cradle. Question: What's the least expensive $$$ using OEM parts (which went 205k miles so far) that I can expect to pay if I just go ahead and rebuild her since I've gone this far?

By your description it sounds like the rear main seal is leaking.

A lot of rebuild parts can be found in the aftermarket that are far superior to their OEM counterparts and for less $$$$.