hi, i also have an 02 tahoe. The stock radio can be used for an amp and sub but to connect the amp then you will have to get an Scosche SLC4, which is a line output converter. All you have to do is splice into the nearest speaker to the amp and use the wires there to connect to the converter. Keep the speaker connected and just use that output from the car stereo for the amp. Once you connect the wires to the converter then you have the ability to run a set of rca's to the amp.
Go check my Tahoe out at
http://www.brainwasheddesigns.com/ki...loads/bump.jpg it is featured on King Kong Customs Custom Enclosure site.