to be completely honest, with chevys, they are difficult to sort out especially from that year, my grandad drives one and he was going to give it to me, but wanted to mod it up for me (this was before he died god rest his soul) and he took it to his friends garage with the new cd player and they had to do a lot of work to wire it up properly, try harness adaptors aswell on ebay, they are quite cheap, not sure if they have them for chevys though worth a try i guess, the work you would need to do would probably be best done by a garage to prevent an accident behind the dash it should be wuite cheap but that would be your safest bet, not the best, but the safest
hope it helps