The DIR-F book is probably a great idea, having read it myself I think I will start reccomending that to my DM students, not that I dive DIR, (Most GUE divers would cringe at the site of my gear setup, although there is nothing wrong with DIR). But, it is extremely important that when you become a divemaster that you are familiar with all kinds of gear setups. I also highly reccomend that any of my DM students take a Nitrox course, even if only for the knowledge not to extend their bottom times. Plus, don't just help with courses, volunteer on a charter boat for a summer.
As for price, I think I last charged around $450CAD for a DM course but from an Instructors point of view you cannot charge enough. The amount of time that goes into one DM (if it is done correctly) is immense. Alot more than $450 worth.
I require my students they have the DM crewpack, Encyclopedia, and most of all an open mind. As for your $700 odd dollars he is probably selling you the Instructor manual and all materials reccomended by PADI. This stuff is important for and IDC but if you are not planning on becoming an instructor right away I would skip it as it will be out dated before you have a DM C-card.
Remember that as a DM or diver for that matter the most important thing is you should never stop learning.