Congratulations to a fellow recent purchaser of an E300DT! I've had mine for a couple of weeks. I love the car, but I've had to do some repairs to bring it back. Here's what I've had to fix:
+ Engine mounts (excessive vibration in the passenger cabin)
+ Replaced front rotors
+ Front struts rebuild kit applied (clunk in the front end)
+ Transmission fluid replaced

Previous owner in the past 10k miles also replaced:
+ AC compressor
+ Water pump

Yes, it also runs just below 80.