I helped a friend pull a dash out of a '98 Suburban a couple months ago. He was just after the dash. The truck was a parts truck. Once we got the dash loose, we just started hacking through the wiring harness to get it out.
I can't remember exactly where the bolts were, but there are only a few bolts actually holding the dash in. Once you get them loose and loosen the steering column so you can drop it down, you can then rotate the entire dash forward to give you a little better access to the wiring harness on the back side.