Indaloman

The drivers door did not lock via the remote. My mechanic replaced the lock but said the control unit also had to be replaced. Lock now works but alarm system, auto wipers and top tailgate locking do not! Mechanic told me to take it to BMW dealer to have reprogrammed. The dealer told me secondhand units cannot be reprogrammed and it will cost £500 to replace. Is this true as eBay dealers are saying units can be programmed. Who is right?