With the wire harness in the link I put up there you do not need to touch the factory harness. You would solder/crimp/tape, whatever you want, the new deck wires to the wiring harness in the link. After all is connected up nice then you connect the harness in the link to your factory harness. Its super easy. No need to cut any of your factory wires.

Ohh and depending on your new deck you will need an attenna adaptor if you want radio stations. All aftermarket decks Ive delt with have a differnt type of attenna socket then the OEM one in GM cars. You can get them online or at radio shack...

Like this one...
http://www.crutchfield.com/p_12040GM...r.html?tp=2569

 

lilwalker20, I second what knightryderx2 said. Get the wiring harness from Crutchfield, It will solve all of your wiring problems, outside of the antenna connection like he mentioned. You can have all the wires connected to your new stereo in your kitchen, go out to the Blazer, and just plug in one harness and the Antenna. Away you go. Their customer service is awesome as well, just in case there is a problem.

 

Thank you guys for your help ill post pictures once i finish...