hi
first of all im sure this has been talked about before but i cant seem to find it anywhere
so if someone can post me a link i would be very greatfull,

My problem is im trying to change the head unit of my 03 vw golf gti , it has the gamma head unit with the factory amp and stuff , whats wrong is there is an ISO block for the power but non for the audio just a blue , green , yellow block ive been to halfords and there "EXPERT " does not have a clue how to do it
im thinking there has to be a converter but dont have a clue what its called a part number or anything

can someone smarter than me please help

thanks