I did this 3 years ago. It's still working great.
Replace the CDR-24 with a modern unit that has Car Play or equivalent. It's fairly easy even with the fiber optic connection. You need an interface for that and a decent new Double-DIN unit. The only thing you really need to wire is a Constant 12VDC, Switched 12VDC and a ground.
You'll need an adapter for the antenna.
What I bought -
Jensen CAR68 6.8 inch LED Digital Multimedia Touch Screen Double DIN Car Stereo
Metra 999606G Porsche 997 2005-2012 DDIN In-Dash Kit, GrayAntenna Adapter
MOST Fiber Optic Amp Interface for Porsche Cayenne Cayman Boxster
