Prices on 126 series cars have dropped quite a bit in the past couple of years.
The climate control problems are the big deal, I think on the car you are looking at. If you have the tools, time and ability to troubleshoot and fix it yourself, maybe not too bad. If you have to pay to have it fixed, could get expensive real fast. Drivers window probably needs a new motor. Not cheap, but can be a DIY for moderate skills. I had to replace the one in my driver side door recently. All the difference in the world.
Only other issue to me is the P.O. being a smoker. Would matter to me, but I'm picky about that.
Other problems seem minor and fixable. Clean the carpets and then order a new set of factory floor mats, front and back. Antenna is $25 or less for the mast. From what I can tell, they all wear tires funny.
For what it's worth: My 560SEL has 342k miles on it. Had it up over 100 recently. Felt great. Cruised at 90 like most cars at 50. Crazy thing seems to get its best mileage over 80mph. I can hear it now "Honest officer, I was just trying to get better gas mileage!"