I would pull the carpet now, or they will not dry out for a long time and will mildew.
what about the water trapped under the carpet and the floor insulation? think about rust.
Dry out the seat tracks and or electric motors. also think about the silt in the tracks once it dry`s and some corrosion starts. of course if your yr 190 has the electric motors they will most likely be toast anyway.
I have seen a few 123`s I tried to pull the front seats. the captive nut on the clip for the rear bolts will get so rusted it and the bolt will just spin.
this is another good reason to take things apart. I would add a dab of Anti-Seiz to the threads.
Isn`t there a electric vac pump under the rear seat for the door locks?
Simpler=Better..... is there a front Differential too? you mentioned the rear diff.
Just funning with you.
Charlie