I have a 2005 Silverado that has a Kenwood DDX512 and amps installed, it originally came with Bose and onstar so I have a GMOS04 behind the radio. The shop that installed this were a bunch of fgts and when the amps were put in they cut the RCA from the gmos. I want to re do the entire head unit install but do I need to connect everything on the gmos and steering wheel controls. Also is my harness still useable even though the RCA have been butchered off at the plug and some exposed wire is there?