I spent today fixing it (better late than never!). After dropping the tranny (leaving the motor installed, with a jack supporting it), I popped the transmission main seal out with a slide hammer. Here is what it looks like on the back - no wonder it leaked!
Here is the new seal installed. I added a couple of other pictures at 914world if you're curious about the process.
While I had the tranny out, I also replaced the clutch on the theory that the tranny fluid would have impregnated and ruined the clutch disk. Which it did. The old disk is on the left, the new (not shiny!) disk is on the right:
I also took the opportunity to put new transmission drain plugs in (the old ones were fairly well stripped, you can see my adventures with them on 914world):
I took it for a quick spin around the block - I think the old oil-impregnated disk was slipping occasionally. I did not notice anything this time, but I'll keep my eye on it.
