The common 210 problems are pretty well known by this point. I'm sure you've been reading up on them in the forum, so I won't attempt to elaborate here. There are not many issues with the 210 that cause reliability or driveability problems; I would expect you are less likely to get that call from your wife than with the 124.

There is no difference between the 2000 -2002 210 cars (2003 if you count wagons). Go for the best combination of miles/condition/records, etc. Don't shy away from an E430 if you find a good one, there isn't a material difference in fuel economy between it and the E320.

Anecdotally, my 2001 E320 wagon has been a good car. Purchased in Sep. 2004, starmarked w/20K miles. Now have 70+K. It's never failed to start, never needed a tow, never done anything that worried me. Repairs I've had done over the course of 5 years are typical 210 stuff - one broken window regulator, a couple flakey pixels in the dash display, a bad MAF, a flaky headrest motor, and a set of spark plug wires. Right now it needs shifter bushings and a new rubber antenna thingy for the telematics. So far I haven't touched the engine - it even has the original serpentine belt, and it looks good.

Other than that, just routine maintenance - A&B services about every 12K miles, one set of plugs @ 5 years, one transmission service. Service is about as easy as any other Benz, and happens less frequently than earlier models. I've done so little work on the thing that I don't really feel all that familiar with it. How's that for a recommendation?