If you find that you need more detailed information than what is offered in either the Haynes or Chilton repair manuals, here are some good sources:

1) Official Factory Service Manual as written by GM.Consists of 1 to 3 large volumes of information. Available from Helm, Inc.
www.helminc.com

2) Online subscription from Alldata. Contains most of the info in the FSM but arranged differently, also lists recalls and service bulletins. One year subscription $25 for one vehicle model, $15 for each additional model.
www.alldatadiy.com

3) Online subscription from Mitchell
$10 for 1 week, $15 for 1 month, $30 for 1 year
http://buymitchell1.com/Merchant2/me...de=eautorepair

4) Online freerepair infofrom AutoZone. Not as good as the others, but it is free.
http://www.autozone.com/home.htm