For most, read not ALL, aftermarket head units, there is a adapter you can get(its part of the wiring) to have it still use the steering wheel controls, and have it show up on the HUD. From personal experience at a car shop, the major brands such as Alpine ect have models compatible for the HUD displays.
However if you had the Typhoon system in your car it can get hairy if done yourself, or expensive if done at a shop.
For clarification, by car shop i mean a place that did custom car work. Didn't work there long since school got in the way of my hours, so some of the newer HU's may not work, i am not sure.
BTW... do you have issues with your volume on your steering wheel controls being way too sensitive? on my 97 gtp its really sensitive.
