R230 Command / Radio exchange and D,A,C Navi CD-where?

Hello, I want to /must replace my crackling command. Where do I get one?Do I have to pay attention to best types (R230, 500, Bj 2002). Where do we move in price? Furthermore, I don’t need a corresponding CD for the integ Navi either… (net technical). Can I please give you a tip? Greeting Marc