98 Yukon radio installation problems. Help?

Just got a 98 yukon and am installing a pioneer radio. I have installed countless cd players but cannot get this one to work. Does it need some special adapter? Is there something that I am missing other than wiring up a GM harness and hooking it up? I am at a loss....

go to www.crutchfield.com..... They will send installation instructions with a purchase or pay $50 at Best Buy or Circuit city and avoid wasting time and money