I am tossing in this picture just in case anyone is interested in seeing leather interior in a 190E.  Looks pretty much the same as a 300E, combination leather/vinyl door panels, leather wrapped steering wheel and leather front and rear seats.
 

Since the 190E came with a cheap looking vinyl shift knob, I found a Zebrano wood shift knob on Ebay which I picked up for $35.  The installation of the shift knob is not as simple as unscrewing the knob from the shaft, the entire shaft needs to be removed.  I did not take detailed pictures of this install (starting to forget things in my old age!) but you need to start by removing the black plastic trim around the Zebrano wood trim cover, you can do this by prying up on the sides.  Once removed you can then proceed to removing the Zebrano switch plate (very carefully) you must exercise caution here, the wood trim cracks very easily.  My trim was already cracked and I purchased a new piece from MB,  After the cover is up, you can unplug all the switch's and put the panel out of the way.  Now the black plastic shift console (the piece with the P, N, D, 3, 2 on it) needs to be removed.  If I remember correctly, there are some screws or nuts that need to be removed, you can then lift this item up out of the way, you won't be able to remove it completely, because of the shift knob, but you need to move it out of the way so you can get down to the linkage.  I also don't remember which open end wrenches you need, but you need to loosen up the nut so you can unscrew the shift knob.  Be careful that you don't strip the nut!  Once it is loosened, the shift knob and attached shaft just unscrews.  Also while you have all this apart, if you have play in your shift lever you should replace your shifter bushings while you have this all apart.  One last thing, check your shift console illumination light, you should probably replace that bulb while your at it, saves you the necessity of removing the Zebrano switch cover at a later date