so i have plans of buying a volvo s40 2011 and i'd like to replace it's boring radio for a carpc with mimics, but i wanna know if i would run into problems if i'm messing with the stock system.
i was thinking that replacing the radio for 7" touchscreen and a amp to power the speakers would be enough, but i have no experience with car audio, i would also like the touchscreen to have volume controls (vol dn, mute and vol dn).

any suggestions or tips are welcome!