I have a few used blower motors hanging around,most were replaced because they squealed like a stabbed pig on low speed when the truck was cold ,and I kept one or two that were good for spares from GM cars I parted out..
--I've never needed to replace one that died completely though--a few that I thought seized up turned out to have drinking straws or pencils stuck in the blower wheel,(or a rats nest !)--or the resistor was toasted...one I had was bound up tight,but after I removed it and sprayed it with some WD-40 and got the fan to spin again,it started working again and never gave me any trouble afterwards..