Yes, the A/C problem is common and quite EXPENSIVE $$$$
My 1995 E320 wagon needed its evap change at 21,000 kms. (the car was only three years old).
The job was very expensive and time consumming. But a good piece of advise I can give you: avoid using the original M.B. evaporator core. They are alluminum made and from the beggining that is one of their design flaws: they rust badly and then they leak!
I had a pure copper evaporator core installed (more expensive, but it is guaranteed for 20 years not to leak). A special aftermaket company in Germany manufactures them, so to avoid the major work involved in changing the part every 4 to 5 years.