The switches for MB seats are made to be serviced; and when done, work like new. Disassemble over a white terry towel (lots of springs and balls).

When open the cleaning and reassembly is intuitive. Just pay attention to how it came apart. The little seat-shaped buttons are even available:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1PF1ACAKH1PF1ACHGQ&year=1981&make=MB&model=300-SD-002&category=O&part=Seat+Knob

I think this may be the easiest way, I hope. Good luck

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)