By replacing the factory head unit with an aftermarket one, will this shut off the volume controls on the steering wheel?

Yes the steering wheel controls will be shut down, but there is an interface aviable at www.crutchfield.com to make the controls work with the aftermarket headunit.

Mejia

YUP Mejia is right. You will loose the steering wheel controls but you get the PAC's SWI-X interface which allows you to use the steering wheel controls in a wide variety of vehicles to command any aftermarket radio with wireless remote capability. Call crutchfield and they can point hyou in the right direction. I got this from the web site

Important Note: Please call a Product Advisor at 1-888-955-6000 before ordering to confirm compatiblity with your vehicle. On some vehicles, you may need a volt meter to locate the correct wires to connect to the SWi-X. The SWI-X is incompatible with many Sony remote controls (see "Detailed Info"). Dimensions: 3-3/4"W x 1-1/16"H x 1-9/16"D. 1-year warranty