Dear prospective owner,
I just wanted to second what Steve, Aaron, and some of the other respondents suggested. ABSOLUTELY have any prospective purchase inspected by an experienced Mercedes technician before making an offer or getting too attached to it. Any old auto mechanic is not good enough. It MUST be an MB tech who is familiar with these cars. They are excellent cars and a joy to own and drive, but if you've never owned an MB before, be aware that major repairs are MUCH more expensive than they are for a Toyota, and require the expertise of someone like Steve or Aaron or their staffs to do properly. This is why the maintenance history and prepurchase inspection are so important. That said, I can say from much personal experience that an old MB will usually run trouble-free for 250,000 miles and beyond if carefully maintained. There is simply no sturdier car in the world.
Good luck!
Colin