Since your insurance company pretty much has to declare the vehicle as salvage, this post is probably moot, but both of our 300E's were flooded about six or seven years ago. The '91 went first, after trying to ford water that was too deep, then the '87 after sitting all day in a parking lot that flooded (much like your 190). The '87 started right up, but the whole way home, the driver's seat was constantly moving (to the full stops!) - on reflection, not something I'd do again.
At the time, both vehicles apparently had enough value that our insurance company was unwilling to write them off. Since that was the case, we went ahead and had the cars refurbished, which basically involved stripping the interior, cleaning it out, and letting it air dry for a couple of weeks. I don't remember what shop did the work, but they did an excellent job - both vehicles came back immaculately clean. They are still daily drivers in our household today, and with maybe a couple of exceptions, have exhibted none of the problems one would expect from having a car soaked in water.
FWIW - If you were to try to repair the damage, it would require much more than opening the windows and sitting in the sun for a couple days. The car needs to be stripped, steam cleaned, and all the electricals need to be checked and/or replaced...