I can only agree with bstreep. My '88 300E turned 204k recently and it still drives like new. Best car I ever bought. If you stay on top of the maintenance and have any work done by a reliable mechanic or do it your self, it will not let you down. I've talked to a mechanic at Hoehn Motors ( MBZ Dealership in Carlsbad, CA) and he told me the service 300E's in 400K range.
Stay with it and you wont be dissapointed.