I'm in the process of doing the same thing in my 06 w/ monsoon. From what I can see, you need this:
GM Factory Integration Adapter
You will lose the date in the DIC no matter what as the DIC pulls the date from the radio (i assume the RDS system). You will, however, be able to keep chimes and everything else with that adapter. Order from Crutchfield and you'll get that adapter for $50 with a headunit purchase.
I'm going to get the Pioneer AVH-3300BT, that adapter, and then the Metra Axxess for steering wheel controls.
