you will need a wiring interface. i dont no if the 97-03s need them. but i got mine off ebay used for 75 with a dash kit. i think its around 100 for it new. you can get it from crutchfield.
like this...GM Factory Integration Adapter General Motors Class II data bus interfaceRetains ONSTAR system, factory door chime, and Bose system with aftermarket radio at Crutchfield.com...
you will only use the wires on the right. its just as easy as installing a regular wiring harness.