I would not recommed buying dan's book, just my opinion, but I think you can get ready without it! I have done a few shows and keep coming in bigger and better. I do own the book, but it has helped me little...what I would recommed is going and watching as many shows as you can before you enter one...make sure and goto prejudging and the night show!
here is a good start...this is the NPC's home page, it has a sample contest diet and workout, tells about rules, posing, testing, etc!!!
I agree with Columbo -- BodyOpus was of little help to me with contest prep. I also know several others who have had bad luck using his system. Contest prep is a lot of trial and error and there is no formula that works for everyone. I think alot of times people try to overanalyze the details of their diet and training routines precontest and end up missing the main points -- lose as much BF and as little muscle as possible.