1998 Audi A4 Transmission control unit and Multi function s

My car started acting up after heavey rains over several days. The transmission indicator began to show erroneous displays, and the car began to shift into gear very abruptly almost as though it was reved up and put in gear at a high RPM.

I was told the transmission control was bad, and had it replaced, but now am told the multi fuinction switch is also bad.

I am simply apprensive, and shocked at the projected repair cost.