2005 Cayenne Head Unit

[Bumbledad]

I had to swap the head unit in my car as the old one died. The replacement seems to be a 3.0 rather than the 2.1 I had and the Satnav no longer works. I have a DVD player under the driver's seat, but the head unit is asking for a CD? The 'new' head unit also looks slightly different at the back with an additional blue antenna socket on the bottom right of the unit. Can I buy a navigation CD reader and do a swap with the DVD reader? TIA