2003 denali stereo upgrade

[hgs_notes]

I just bought a used denali. It has the premium sound system from the factory and it works but I have gotten used to having the bluetooth for my phone and an aux port to plug my mp3 player into. I've looked at a couple head units, I don't need a touch screen, so a double DIN head unit with CD and radio is fine with bluetooth and aux ports.

My question is, how hard is it to install? The head unit itself is no big deal but I want to keep the steering wheel controls. I know there is a wiring kit for it.

Another possible complication is that these older models have had the onstar disabled because they were analog systems and no longer supported, and the factory stereo has rear seat controls also. I think there is a factory amp connected also.

Crutchfield sells an install kit that includes the wire harness for the steering wheel controls. Is that all I need? I saw a youtube video where a guy also had an onstar adapter, but it was a few years ago and I don't know if thats something I need or not.

I could take it to best buy or another car stereo shop for install but they want around $250 just for the install (more than the cost of the stereo), which seems ridiculous to me.