I have never touched a 190E, but I've had W126 seats completely apart, and suspect that what I'm about to say is true for your chassis also...
In a W126, you can divide the front seats into 4 parts-
1) Rails between floor of cabin and seat, held in the car by four 10mm bolts
2) seat bottom, which includes horsehair and cover
3) seat back, again including the horsehair and cover
4) armrest
The frames, pads and covers on 2) and 3)** are the same on both sides- you absolutely can switch them. However, the rails are NOT the same- there's a do-hickey for the seat belt on the right of the driver's rail, and the left of the passenger rail, so you'll need to swap the rails. Also, you'll need to switch the armrest from the passenger seat to the driver's seat. Swapping the rails is sort of a pain, because you need to scoot the seat forward and back on the rails a few times to get access to all the screws (USE A #3 PHILLIPS). Swapping the armrest is easy- you just need a 27mm socket, and you need to remember to switch the metal reinforcement piece from the driver's to the passenger's seat.
You'll probably want to verify that this applies to 190 seats before you attempt it... If I were you, I'd log on to
https://epc.startekinfo.com/epc/ and check to make sure the part #'s for the driver and passenger side seat frames are the same. That's how to be really sure that it will work. Good luck!
**Except for the cover on the back of the seat back, but those are trivial to switch. Also there is a hole in the side of the seat cover of the driver's seat to allow attachment of the armrest.