My two cents:
Your tech seems knowledgable enough to distinguish a rear mail seal failure from a failure in the area of the oil pressure sensor or oil pressure port. I don't know if your oil pressure gauge is electrical or mechanical. No reason to touch the rear main seal or oil pressure sensor during a timing chain job.
The next major expense will probably be a valve job. Depending on current oil consumption, you might get a few more miles out of it by changing just the valve seals.
Even with regular maintenance your tranny will be on the luckier side to see 150K miles without a rebuild.
I can't comment on the longevity of canvas tops and stowing mechanisms.
There was a front subframe recall on some 107s. I don't know if it applies to your car.
Even when dealing with the best techs, there is a strangely high likelihood of something breaking right after picking up the car. The AT kickdown switch in my 91 SE decided to stick within 100miles of having my tranny rebuilt. My tech made no worthwhile money fixing it. In your case, what tech has the time to drop a tranny to poke holes in a rear main seal? Yet how strange that things like these wait until you're driving away from the shop to give up the ghost.