Thread: New and need help

I am new to this forum so first let me say hi, so HI!
I have a 2004 Grand Prix GT2 and I want to replace the stock Monsoon system (just stereo, not speakers or existing speaker wires) with a Sony CDX-GT55UIW. I know we will have to purchase a wiring harness to keep all the chimes and other doo-dads that are hooked in, plus the adapter for the steering wheel controls (Metras Axxess ASWC). But I am not 100% sure which harness is best. Most recommend the GMOS-04. Is this what my model needs? My model did not come with OnStar, so is there a different GMOS I need? I found both the harness at BestBuy and the adapter at Amazon.

I am trying to make this as painless as possible for my husband, I am only the research assistant, hehe. I also want to know what info I may lose on my DIC, I am not concerned about the date as some said they lost that, but want to keep my other warnings and controls. Will this harness help me retain all that?
Any help is appreciated. Main reason for me wanting to switch out head units is the Sony is IPOD friendly and the 6 disc set ups have been known to eat cds, plus with the IPOD I wont have to haul a case around.