Chevy Avalanche subwoofer/ipod connection?

you will need to buy a interface for your stock head unit to connect your ipod unless you go with a fm transmitter which are crap chances are you will need a line out converter for you amp as well you should look into a new head unit it sometimes will cost you less than trying to connect to stock unit keep this in mind as far as cost for installation be prepared to spend around125-200 for the amp shop around for best price also if your having someone install it for you let them do it all it will not save you much if any money to run 1 wire yourself