Aftermarket NAV in my new H3

[Hummerguy04]

I just purchased a 06 H3 with the Monsoon stereo system. I have a Pioneer AVIC-N1 that I originally bought for my 04 H2 with Onstar and Bose. I traded the H2 for an 05 Chevy Avalanche that also had Onstar and Bose. The interface harness I used in my H2 and Avalanche was a Metra GMOS-04 and it worked flawlessly. When I would use the Onstar it would shut the aftermarket radio off until I was done using the Onstar and then turn it back on. My question is the Metra GMOS-04 compatible with my H3 with Monsoon system? If so how would I adjust the onstar volume because in my prior two vehicles I would use the steering wheel volume control but the H3 doesn't have steering wheel controls, which really surprises me. If it isn't compatible what are you guys using to retain your Onstar while using an aftermarket radio? One other thing I liked about the Metra piece was that it retained Onstar, Bose amp, and all the chimes in one single module. Any help you guys can offer would be great. Thanks, Scott.