Wear dated parts bound to wear out
Overall I would have to look at the car as a whole looking at parts that will definitely need replacement. Generally a car this age has probably been through a change out of a lot of parts that generally go out in the 100-150 thousand mile range. Things like starters, alternators and the like are generally unforseen problems that just happen and aren't considered a routine maintenance change item. Heaven no, I don't think I'd change out my alternator just because it had 175,000 miles on it. In most cases these items either show that they are on their last leg, or they simply go dead out of the blue. Even the seller can't predict the future of his car. As Bill mentioned though, these are easily replaced items, and in most cases aren't to awfully expensive to buy. If you are convinced the engine is strong and the tranny is solid and the major driveline is stable, then the decision to buy this Benz solely rests on whether it captures your desire to own it. Trust me, there are a hundred little things that could be wrong, and all of them could add up to $500 in part costs and several hours in labor on your part, but in the end it's good for another 100,000 miles. How many U.S. made cars out there last through the warranty period without a glitch where it has something major go wrong with it? I'd say none. Personally I believe that both of my diesel powered Benz's both with over 160,000 miles are just now getting broke in.
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan