its not bad. I ordered a new one from GenuineAudiParts.com, bout $45 iirc.

you just pop off the wood part around the shifter and then use a screw driver to reach in and push up the old knob from the bottom...

from teh Bently:


Mirror adjustment switch, removing and installing

Removing in vehicles with automatic transmission:




-Pry center console insert upward and off.

-Carefully insert a screwdriver in the hole at right next to the two mounting bolts for the center console.

-Once the lower part of the mirror adjustment switch -1- is felt, lightly press mirror adjustment switch using the screwdriver and pry it out.

-Disconnect electrical harness connector -2- at mirror adjustment switch -1-.

Installing

-Install in reverse order of removal.

Note:
When installing, be sure that no retaining clips are missing at front or rear of mirror adjustment switch.