I just purchased a 1976 300d and I am wondering if there are any issues with this model I should look for. The car is clean, inside and out, and only has 75300 miles on it. The dealer got it on a trade in and sold it to me for a respectable amount - but an amount that was definitely in my favor, as he really wanted it off his lot. I have not owned a diesel before so I am a complete novice to mercedes cars. Any suggestions?