Passenger seat does NOT move up/down, only forward/backward/recline.
The car not starting is most likely the "mystery no start" scenario, 3 lugs on the RCM ( Relay Control Module ) need to be cleaned and re-soldered, easy job.

Did you check the rear window bond ? This has been an issue with the roadsters.

As to the interior, I can't say other than there are numerous good products to restore the leather.

Here is a list of items to be inspected/replaced IF you buy the car with 77K miles:
1. fix the RCM.
2. replace the CPS ( Crankshaft Position Sensor )
3. replace the serpentine belt.
4. Change the oil & filter ( Mobil1 0-40 - 8 qts and a Mann fleece filter )
5. flush cooling system and replace with 50/50 Zerex G05 / distilled water.
6. replace the plugs and plug wires ( needswings.com )
7. replace the air filters and the cabin filter.