97 benz ryder

My ecm case is broken and won't lock into place. which is causing some of my electronic not to function properly(cooling fans and ac). had it checked and the shop said it was getting fire to the box (ecm) but not from the box. They told me to get a used ecm but the dealership said it won't work because its married to a particular car. Just wanted to know if anyone may have had this same problem and can i get a used one. Or is it possible to put mine in a new case so it can lock into place.