HELP!! e36 m3 smg - manual coversion started!!

[ALS M3]

im running an m3 thats already had the conversion done but using the original smg box, it does work but it doesnt have the detent springs fitted and not very nice to drive so i have just purchased a proper 6 speed box.

does anybody know if this is a straight swap as the garage thinks i might have to swap the ecu with the car originally being an smg!!

and can anybody fit me the detent springs to me smg box ??

cheers