John is on the right track.
Get an inspection by a good indie, if you're a long-time benz pilot you have to know at least one.
My concerns would be exactly his: not driven enough, particularly so if they were short trips spaced out. This is a 12-year-old car, so that's not much more than 1,000 miles per year or less than 100 miles a month. If it was only driven three times a month for 33 miles per trip that would be fine, but if it was driven 20 times a month for five miles per, yikes
At the same time, so long as oil changes were done regularly, there should be no hard parts damaged by this, leaving of course the concern of the seals and gaskets, which tend to dry out even when used over a 12-year period, much less when left parked much of the time. Having to tear off all exterior parts of the engine to re-seal and re-gasket it would not be cheap, but it also would be lots less than a rebuild. Of course you also have to consider the other seals and gaskets, such as those for the transmission, differential, wheel seals, fuel system, brakes, etc.
A good drive (50-100 miles at moderate speeds, but only drive it about 20 before stopping to check and see if anything looks really bad that quickly) should reveal any significant leaks, and after that drive, the indy's inspection may be more revealing -- assuming there is anything really ugly to find.
Post back and let us know the shake-out.
Take care and enjoy the ride,