It is the Winegard box that is connected to the dish that can't find the sats. A receiver is not needed and has nothing to do with the dish locking onto the sats.
Not really. The logics that allow the antenna to lock onto the satellite are located within the antenna mount itself up on the roof. You are correct that a receiver is not needed to lock onto the satellite but the controller inside the coach is just shy of a "dumb box". It either sends a message to the roof telling the antenna to do something or it receives a message from the electronics on the roof that it has done something.