Alpine car stereo touch screen

I think I pretty much already know the answer to this one, but thought Id ask just incase!
In my car I have an Alpine headunit with 7" touchscreen.
Obviously my initial thoughts were to use a Pi with it for sat nav/music etc, but if that was the case I would need to control it all.
Does anyone know if it would be possible to use the touchscreen aspect of the screen to control the software
Im guessing not as there would be no way to interface it with the Pi
Im not sure if I want to remove the stereo in place of a touchscreen that would work as I also have ipod connectivity (not such a problem as I could use a external drive with the Pi) but also have digital freeview tv which would not work with the Pi either

is the touchscreen built in the car dashboard or console?
if so then I highly doubt it without taking apart your car and modifing internal connections and voiding your warrenty

if not
then it is possible.

What I recommend is that you use a cheapy portable dvd player that has away to connect to another monitor and plug the raspberry pi in the cheap monitor using the provided cable.

P.S. I was also thinking about a set up like this