I own a euro C-class as well, although my car is a 1993 "classic". You can imagine that it had completely nothing
(besides the sunroof).
I changed my complete interior from blue cloth to gray leather and from black plastic trims to faux carbon ones (they look good though).
I presume that you know that leather door panels with manual windows were not possible with mercedes? The leather door panels are fluffy and the manual window crank would damage the leather...
If you get yourself some OEM leather door panels from the later W202, you can change them anytime.
The older C classes did not have side bags and these panels are not very suitable
(the complete door panel is different, so I think you do not want to have those older ones anyway)
The OEM door panels have the trims attached to them and if you want to, they are exchangeable...