Here's an update on progress with the Benz... in case anyone has the same issues that we did. Also, thanks MTI for the help!
Heater core (FIXED): The Haynes manual and http://www.benzworld.org/forums/w201...01-heater.html
were huge helps. A long job, but nothing particularly challenging to do. Fitting everything back together was a pain, since the foot vent pieces that sit under the heater housing did not want to fit back together right. Did not have to remove the steering wheel at all either.
Alignment (FIXED): Replaced passenger's side ball joint using a two-arm puller and the autozone ball joint rental tool. The job took a while, but everything went smoothly overall. It's a real pain to remove and reinstall the coil springs (those things are huge compared to the space they sit in) with the cheapo compressor I have - if I did it again I would try to put a compressor on to hold the spring in place (and a jack under the control arm) and do the whole job with the spring still installed. One nice side effect: I found and repaired a frayed ABS sensor wire while I was in there and the ABS now works again!
Also replaced tie rod ends... or rather replaced the tie rods. The outer rod ends on both sides were bad, but unfortunately were also so frozen into the tie rods that the rod ends actually sheared off before they would turn. I guess that's what happens after 22 years. Found one junkyard tie rod in good shape (replaced the ends), and bought one new one to put it all back together. Steering is much, much tighter now than it used to be.
Door locks (UP NEXT): still non-functional. It seems that the little bits on the end of the lock cylinders are also cracked, which I assume are what actually operate the locks. The passenger side one is getting the JB-Weld treatment right now, and I have yet to pull out the driver's side lock cylinder. Vacuum pump is still not operating at all (before the wiring for it was bad, now it should have power but isn't actually running), but I've got a spare from the junkyard to plug in and test.
Transmission (STILL QUESTIONS): Still shifting super-early. It turns out that the dipstick itself broke at some point (?!) - snapped off at the "high" notch on it. Got a new dipstick from the junkyard and the fluid level seems a bit high. Previous owner said he changed the filter/fluid in April so I'm not worried about that, but my guess is he filled it too much because the dipstick had no markings on it! Could this be the problem and is there a way to drain just some of the fluid?
Two other major things that have been fixed up:
Fuse box: Someone (dare I say idiot) apparently decided a few years back that the fuse box cover was unnecessary. As a consequence, there was quite a bit of corrosion in there. Fuses 12 and 13 were not getting any power. Luckily they are ones that run off the battery, so I spliced in two wires and a couple blade fuses to cover for them. Suddenly all (well, some of) the accessories that were inoperable before have magically started working. A new fuse box cover from the junkyard is also working wonders.
Rust: Rust, rust, rust. The car has spent its entire life int he northeast, so no real surprise here. All in all, it's actually done pretty well. Front passenger's side jack point was particularly bad (spread into floorboards) but is all welded up and should hopefully serve for another couple decades. Possible cause: the little rubber overhang that deflects water on the passenger's side of the hood was missing and could have been letting more water/salt in than would otherwise be. Possible resultant problem: vacuum lock troubles. You wouldn't believe the amount of damp sand we pulled out from under the rear passenger's seat. Haven't checked the wiring extensively yet, but I'd be willing to bet that the hole in the rocker panel contributed to the downfall (via corrosion/shorting out) of the vacuum pump. The other jack points are rusty too, but nowhere near as bad as that one.