Upgrading Aftermarket.

I just bought this 2001 Suburban K2500 4x4 , I don't like the factory CD Radio and want to install navigation unit that's 2din. I checked a few website's that tells me the opening in the dash is 1.5Din. I was told I could use some 2din units like the pioneer AVIC D3 and maybe the AVIC -Z2. Also tried a few shops that said they could do it with medications to the opening. I guess that means . lets pull out the dremel . It seems to me that a 2din could fit without modifications, at least for the Pioneer AVIC D3 has any one done this. ? if so what nav units have you used. Also this 1.5 din measures 3 7/8 x 7 7/8 or 8" with the dash trim on. Is this opening in the dash really a 2 din size for this 2001 Suburban 2500.