Has anyone replaced their head unit and not used the expensive wiring harness adapter? I've replaced head units in many vehicles (granted mostly older models) and never seen a $130 wiring harness adapter like the one Crutchfield claims I need (http://www.crutchfield.com/p_120OSLAN01/Axxess-GMOS-LAN-01-Factory-Integration-Adapter.html). I don't think I will miss the door chimes or turn signal chimes and don't have onstar or XM so I'm wondering if I can get around using this harness and hard wiring everything or if this will just cause me more headaches than it's worth. I'm putting in a 5 channel amp and new speakers all around so I'm not worried about the connection between the head unit and speakers. I know with a little rigging I can get the head unit to work, I just don't know what else I may lose functionality of. I also don't want to make it a complete pain in the a$$ to swap the factory unit back in, in case I decide to sell it but it shouldn't be horrendous from a wiring perspective to tap into the power and ground, speed sensitive sound control wire, and illumination wire of the factory harness to power the head unit. Has anybody tried this get around or is it just worth it to bite the bullet and buy the factory harness adapter? If I buy a +$120 head unit from crutchfield, the adapter is half price but that still seems like an absurd amount of money for a little wiring harness that I won't be using 90% of the connections for since my speakers will be wired direct to the amp. Any help would be greatly appreciated. Thanks!