I already have a DVD player and 6.5 inch t.v in my car mounted in the dash. I was thinking about adding 2 more in the headrests. However I won't them to be able to play movies and my dreamcast. Is there an a/v type switch I can but somewhere that will allow me to switch the inputs. How hard is this to connect and install. I plan on doing the installs myself, thats why I am asking.