Hi,it has been a long time since I've had one apart but I think you have to drop the portion of the dash with the switch in it to gain access. There should be two screws at the bottom hidden behind the ashtray and two screws at the top hidden by the center dash vents. You may have to pull the center vent nozzles out using a hooked tool ( caution, the little spring that tensions the nozzle will probably break off ). Once that portion of the dash is down the wood trim around the switch has to be pulled off using a hooked tool ( caution, the wood may crack or break ). Once the wood is off there should be two screws holding the switch in place. I know this seems like alot of steps but it should only take a few minutes.

Good luck, Robert.

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Mercedes Benz Master Tech - Retired