I've read frustrated reports about installing a wood shifter knob on the 190e. I did mine yesterday, and can report that for me at least it was not a big deal. I didn't spend over ten or twelve minutes on it.
You lift out the wood console surround, which is just a friction fit, and unplug the switches. My car, a 1991, has three tabs holding the cover on the shifter, which I popped loose with a flat screwdriver. I have read that some cars apparently have four screws that hold it down. The cover lifts away and you have access to the 16mm lock nut holding the shifter stalk on. (Stalk and knob are one piece; we're replacing the whole thing here.) Loosening the nut allows the threaded stalk to turn, and it's out pretty quickly.
You just run the cover up the new stalk, thread the locknut onto it, and then screw the new stalk/knob in where the old one came out. The knob needs to point a little further to the left than I thought it did, to get it to come out straight when everything is back together. When it's positioned where you think it should be, tighten the lock nut and pop the rest of the stuff back in place. I had to undo it once, to reorient the knob. Simple.
I hope this helps someone in the future.