ok i want to install a cd player hed unit in my 80 f100. i need help with what the original wires are. i have a round harness and 4 wires leading to the original radio. the wires are red, green, black, gry. i have very little experience with electronics and head unit install. i want to install a newer headunit with cd and maybe add 2 more speakers. what i wnt to do now is just remove the old original radio and put in my few year old cd player. any help will be great.