You are correct about CP . Taking your cd changer to a hifi/pc repair shop could be an option as they test it or clean/change the laser at a fraction of the price. You would not need to worry about cp if it works
Intresting...Ross tech ( people who make vag com ) recomend codding new battery so the system knows the parameters so it wont overchange , also if its not codded it may not show battery status correctly