cb radio or cd player add on? just want to be clear. post a pic of what you have currently. you can get the factory stuff in all kinds of combos. radio, radio with cassette built in, radio with cd built in, and with plan radio or cd/radio you can get the separate cassette module.
if you are looking for something more advanced then you can go aftermarket.
ask yourself this: are you happy with factory equipment? do you want radio with cd built in leaving the lower pocket for storage perhaps. your answer will determine which oem part numbers, configuration and any change in wiring needed. in general any device in the lower compartment is is tied to and controlled from the main unit.
now if you are talking citizens ban radio we have to start this convo over.