Chevrolet Malibu Transmission Replace/Remove

I Wanted To Know If You Install A Used Transmission In The Vehicle Do You Always Have To Have It Programmed Or Only If It Does Not Work...

My 2004 Malibu Maxx - Still Under Warranty - Has Been At The Gm Dealership In Floral Park Ny (hudstead Chevy) For Over 40 Days!!!! After...