I'll second Matt L's concern about the price for that mileage. But these cars are uncommon, so the law of supply and demand suggests you may have to pay a premium for the diesel instead of a dime-a-dozen E320. I'd check ebay (current and recently closed auctions), cars.com, and your local Craigslist to get a better sense of the current market. Ask your mechanic, too.

Assuming whatever mechanical inspection you can manage doesn't reveal any obvious problems, for that price I'd want a car in pretty fine cosmetic condition. If the paint isn't near perfect (i.e., garage kept) with absolutely no rust (look carefully around the doors and trunk; lift the rubber weatherstrip), I'd think twice.

If you search the forum, you'll see a principal complaint of rusting front spring perches on the W210, which is a safety issue. Verify that they're either rust free or have been replaced. Also familiarize yourself with the breaking glow plug issue (search for OM606 and glow plugs), which is a concern but not necessarily a reason not to buy the car.

While I respect Matt L's opinions, I'm going to have to call him on his statement that the 245K transmission is "probably good for more miles." I'm not saying he's wrong, but I'd like to know what evidence he based his conclusion on. I'm no expert, but how many Mercedes have you seen with more than 250K-300K on the original transmission? I'd reserve judgment until I actually drove it and looked at the service records (which, we hope, show regular fluid and filter changes). Even then, I'd throw $10 in a jar every week to hedge my bet.

Personally, I wouldn't worry too much about this model being "driven hard." It's a non-turbo diesel, for crissakes, not a BMW. You'll see what I mean when you test drive it. As my brother says, "It can get out of it's own way," but it's not the kind of car an aggressive driver is likely to buy (or keep for very long if he did). Dealer servicing for two owners says something, too. And if was driven hard on the highway, so what? It's a Mercedes diesel. Mine isn't happy until it hits 80.

Good luck.