I found this on another list:

The model 140 S-Class sedans and coupes are equipped with a very sophisticated HVAC system. There are three separate air filters in the system. The service department at my local M-B dealer gave me a quote of $1100.00, parts and labor, to perform this job. I ordered the parts for a total of $566.00, including shipping. Spending a few hours of my time on this procedure allowed me to put $534.00 of folding money back into my pocket, and gave me the satisfaction of a job well done.