It's certainly possible to swapout the headunit, but as the aperture is only single DIN size, you're quite limited in what you can install. While there are touch screens available which will fit, double DIN units are much more flexible.
Personally, I'd be looking at a good quality (Clarion, Kenwood, Pioneer, etc) headunit with bluetooth and using the phone for navigation, music, etc.
I installed a Pioneer MVH-X380BT in my old Punto which was great.
Thanks for that, I did do a little research as well and yyou are right a decent head unit would be probably the way to go unless you have unlimited budget,.