I'm sure there are books about body work but I don't know of any specifically about Broncos. Use this forum as well as others and you'll be fine.
I started my project last Aug with no previous body or welding experience and mine came out fine (more than few booger welds but otherwise okay). Check out
http://www.colorado4x4.org/vbb/showthread.php?t=151101
A couple of things to watch out for:
1.) Do one panel repair at a time
2.) If necessary to do more than 1 panel at a time, brace the body
3.) Use sheetmetal screws to pull panels together for good seams
4.) Measure things umpteenth times before welding