Just wondering if you can take out the stock head tuner and replace it with a common aftermarket one??

http://static.howstuffworks.com/gif/autoreview/400x266/2000-Hyundai-Accent-00803011990001.jpg

Yes you can, you just need the bracket adapter that holds in the stereo and a wire harness that fits your car.

http://crutchfield.com/c_3/Car-Audio-Video.html

Crutchfield can help you find what you need for your car. But afterwards shop around, as Crutchfield can be expensive. You can also go to the store and they will be able to help you there.