Is Head Unit Necessary??

I just have a simple question. Is the head unit for the stereo in a 2000 and up impala needed for day-to-day operation? I recently installed an aftermarket in dash cd-mp3 player. It's been about a week and the car runs the same and I have had no eletrical problems. The door dingers and all other warnings are still working as well as the factory security system. Is the head unit needed or can I just sell it and get rid of it? :sly: