I would be ware of a dealer who said you required complete unit. Here is my guess and it is ONLY my guess. The recirculator door, defrost door, are usually controlled by a small motorized unit. This is how most all fords made around that time work although this car started out from a Jaguar so there is a lot of English design especially in the 2002 so I don't know for sure. For you to need a complete system just doesn't make sense. That would mean a new
compressor also. It sounds to me that you May have an electrical problem which is common in these cars. It could be as small as a fuse or at worst, the Front Electrical Module (
FEM) which is the brains and controls most of the systems inside vehicle. I would look for another opinion from a reputable repair facility if you can find one.
I hope this helps and you get more opinions other than just mine.