1. Visit Seldon's Philmont page (http://www.lns.cornell.edu/~seb/philmont.html
You'll find links to almost all relevent Philmont sites.
2. Subscribe to the Philmont email list (http://www.usscouts.org/lists/Philmont.asp
You'll get answers to all of your questions from some very seasoned (and I mean that in a good way!) Philmont trekkers.
3. Purchase COOPER WRIGHT'S & WALLY FEURTADO'S PHILMONT ADVISOR'S GUIDE (mailto:CoopWright@aol.com?Subject=Philmont Advisor's Guide)
Indispensable, in fact, do this first. Coop will email you the Word document and include instructions where to send the donation (410 I believe).
There are many more links and sources, but these three will point you to want you need or to where you can find what you need.
BTW, we hiked Itineratry #2 this summer. We were all beginners and it's one of the more moderate treks. But don't fool yourself, even the easiest Philmont trek is a challange, especially for adult advisors. Hiking across Tooth Ridge on our second to last day is one of my most memorable moments. ahhh (BTW II- our troop didn't get a 2006 trek. Now we're waiting to see how far down on the waiting list we are)