[21sH2]

yes there are a few harness' that you will need/want. There is a harness for keeping the bose system, the onstar system, and the steering wheel controls, as well as a dash mount kit to place the mounting screws in the right place and a couple harness' for the navi to the stock harness......i did mine a few years ago after purchasing it and the biggest PITA is after getting all the wires hooked up, finding a place to stuff it all in the dash. lol You would think there is plenty of room behind that monster of a thing but its actually pretty tight with all the harness'. I installed the Pioneer avic system and love it, yours might not need all those but thats what i used to retain everything it had stock.