Some of my comments agree and disagree with A. Rosich.
I would look out for only two real areas of concern:
1. The engine wiring harness. They are bad on all 1993 - 1995 300E / E320's.
2. The head gasket - the early head gaskets leak oil at the right rear corner of the head gasket.
I have seen / heard / read of very, very few problems with the automatic transmissions. The transmission with problems was the transmission on the 1997 E320.
Evaporators failures are fairly rare on the late model W124's. The failure rate was common on the early 300E's, i.e. 1989 and earlier.
In southern California, I look at the ads daily, and 1993-1995 300E / E320 convertibles go for between $25k and $35k.
They are also ranked by Frank Barrett in his Illustrated Buyer's Guide to Mercedes Benz as a four star vehicle. There are only 2-3 cars that have 5 stars for collectibility in Mercedes' history, and only about 10 cars in the history of Mercedes Benz that were awarded 4 stars. And in the modern era, only the 500E / E500 and these convertibles were given 4 stars.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".