I must place a link for everyone here.
Instead of purchasing a separate Control Units for each stereo/installed feature in our vehicles (steering wheel control, Chimes/blinker Unit, and Sat/Onstar)
Check out Metra Cmos-100 unit instead
Metra Electronics - Dealer Parts Warehouse
Whether the vehicle is amplified or non-amplified, equipped with satellite radio, Onstar, Bluetooth, or steering wheel controls, the GMOS-100 can retain it. All the warning chimes and convenience features are retained that are normally lost when the OEM radio is removed.
So regardless of the extra features, the configuration you have, or what you want to install, this all in one unit can serve all your needs. Plus this unit cost only $150-175.. So you will save money compared to purchasing the 3 separate units which cost around $50-100 each! Plus since it's a single control box, it is much easier and less confusing to install since you don't have to find a place to hide and wire 2 or 3 separate control boxes in our limited space.
Also for those who use Nav/VSS systems and find it a nightmare/inconvenient to install...
The GMOS-100 also provides a 12 volt 10 amp accessory output and outputs to help install a navigation radio which include VSS, Parking Brake, and Reverse.
P.S. From the wording in the Manual, it may seem like you still need to purchase a wiring harness specific to your vehicle, however, they are all included in the set.
Also here is a website with the best price of $150 and free shipping