Leather was offered as an option on the 190e (with the exception of the Sportline and/or Limited Edition models, also the 86-87 16V had it). That said, it is quite a rare option, almost all 190e's came with MB Tex.
The biggest thing on the 2.6 (m103) is the head gasket/water pump. Other than that they are great cars that will last a long, long time.
As for the door panels, it seems that in any climate where it gets excessively hot the door panels tend to peel away from the door, especially around the arm rests. I have not seen anyone come up with a good fix as the MB Tex must shrink with age and it is nearly impossible to get it back into place correctly.
If you are familiar with the 124 (as your signature indicates) the 201 will be second nature as it is the 124's little brother.
Check out
www.190revolution.net for a forum completely about the w201.