HELP 2000 S430 Transmission

[Ballroomman]

Long story - butt i purchased a 2000 s 430 with 28000 miles on in. the car was a flood.
the transmission wont shift out of 2nd gear.
on the way to the store it will shift fine , it bumps down into 1 funny. the trip back from store it doesent shift again
it did this a couple of times.
we changed the transmission control marginal ( no diffrents)

MB shop does not know what to do. they already have $ 2000 in *search cost* but the woud like to replace the entire wiring harnesss for $6000 and up.

now i know waht you are gouing to say about flood,butt please just help this time