Toyota Yaris ECU & gearbox Problem

[rpf]

I have a 2007 Toyota Yaris Auto gear car which had a reverse gear malfunction and took it to garage. Upon trying to fix this issue from the garage the car did not start at all. The garage couldn't figure out so they sent (in a carrier) the car to the local Toyota company in the area who at first couldn't figure out why the car does not start. However they came to the conclusion that the car's ECU has gone. With so many attempts to repair it, it couldn't be done and the Toyota company's initial suggestion was to import this part (which would take atleast 2 months) as we couldn't find a second hand ecu locally. After desperate attempts to find a second hand ecu, we finally agreed to import the ECU and while trying to place the order the model numbers did not match and they said to us that this car was originally a manual gear car which was converted to auto gear.  SO replacing a ECU would not guarantee that the new ECU would match this car due to the complicated situation.  So we heard through a friend that replacing the whole gear box might just solve this situation as it comes with a new ECU and the whole gear box is replaced. I just want to know that replacing the auto gearbox itself will solve this situation and be able to start the car once again?  

Thanks.