I bought my vibe in 2010 and in about 2013 the buttons on volume button broke. I had it replaced and 6 months ago it broke again. I am officially done with this factory crap stereo and would like to replace it with a new one that has MP3/Bluetooth/USB support. When I spoke to an installer he told me I needed a GMOS-LAN-012 harness which I bought second hand. I also already have a stereo as well as a dashkit. What I want to know is do I really need to install this GMOS harness if I don't use onstar at all. I've never even activated it. If I don't need this particular item, do I need a different aftermarket wiring set-up? Also, how complicated would be to do myself if I already know how to get the panels off? I can't justify the $200 I was quoted for an install. Not if I can do it myself. Thanks for any help in advance.
Edit: My car is the base model. No steering wheel controls or premium sound.