1997 e320 (P0730) incorr gear ratio

Hello everyone I have a 1997 e320 w210 with a CEL on code (P0730)INCORRECT GEAR RATIO and is now in Limp mode drives in 2nd i believe and doesnt shift.Clunks when i put in reverse and drive..The cars mileage is 100k and I recently over flowed the tranny with atf because the first shop there was so much it was leaking so I then replaced the conductor plate,ATF Plug,gasket and filter at a shop that's now telling me it needs a new tranny.What they failed to tell me that my transmission control module was soaked in atf that I found when researching and decided to check.I removed the tcm and cleaned it with MAF as well as the connectors.Now waiting to insert everything,clear the code from the tcm and give it a try.Please anyone know why I'm getting this code and what else I can do to fix this car.Thank you all so much for your help