Was able to work for just a little while tonight.

Drained some transmission fluid off, and after going through the proper procedure, found that it had been overfilled by more than a quart. No more leakage was observed, but the car remained on jackstands tonight.

Hooked up SDS/ DAS, and cleared out a bunch of old fault codes and adaptives from the TCU and other modules.

Weather was bad here tonight, so no test drives.

Car would run about 219° at idle with an 80° ambient temperature. Too hot! Tomorrow I will attempt to fit a W203 fan (thanks to @Dave2302 from SLKWorld!). My initial preference is to turn it into a pusher fan and put it in front of the A/C condenser, but that probably has a less than 25% chance of success. After that, it will be time to relocate the radiator, much like Dave did on his SLK project.