Mos likely youse be right.The switch is bad.
BUT,first what shape are the Bushings on your shift rods in?
The question about prognosticating the date of total disfunction is beyond
the scope of almost all the Humans on Planet Earth.
IF the Transmission is the original (or an exact replacement) The Mercedes
VIN number is the preferred determinant for parts number selection.
FREE,FREE.FREE
Electronic Parts Catalog
FREE,FREE,FREE
They will ask for a U.S. based credit card number to verify you're one of their
customers...No Charge against the Card ,though.
FREE,FREE,FREE
http://epc.startekinfo.com/epc/subscribe.jsp
(plug in Your VIN and hit ENTER,VOILA parts Numbers)