You won't be able to really "add on" features to the stock head unit...if you want this stuff, yes, you'll need a new head unit and with the proper harness adapter it will just plug right up to the car's wiring. I did this with my '03; replaced the factory head unit with an aftermarket one, used the correct Metra harness, and voila. No muss, no fuss...left the rest of the factory system intact. I'm no audiophile so I didn't have a need to go taking the car apart and changing speakers and amps and all...for me the factory setup was good enough. I just wanted the additional features like Bluetooth and such. Not to mention my factory CD changer ceased to function properly anyway.