The system you are looking at is fitted with a MOST system, you will probably find that if it has a factory fitted phone kit it will more than likely to be that, which is in the passenger foot well, if you don't know how to test the MOST system then you have no chance...
If it is the phone module, then the new unit will have to programmed and coded, or it can be removed, and the you will have to configure the gateway and MMI unit.

Milan