hello...i just got a ml500 2003 for my wife.the security code comes on 5 digi numbers..cant find it no where.my mechanic took the radio out to get the serial number so he can call mercedes , but it was scratch off and it had no nav...so he told me that someone took the original radio with the nav and install one from older model like 320 without the nav..there's anyway i can get the radio to work any steps i need to do to clear the code..or just buy new unit..any help i can get will realy help thank you guys...