id suggest a good hydration pack....its nice to have water whenever you need it....power bars are also nice, as they have a good amount of carbs and protein and serve as a great snack!
some nice, light, fenders are good. id also invest in a small computer, with a speedometer, odometer, clock, and possibly a heart rate monitor too.
an LED bike light may be useful too. the good ones have an extremely long battery life, as they use Lithium ion batteries.
I would suggest a brooks b-17 saddle. Get on now and start breaking it in. As far a as bike go to www.xtracycle.com and get your a Big Dummy by Surley. There a three guys bike the spine. Thats from up near the Arctic down to the point South America. They are using products from xtracycle and there web site gives you tons of info. ridethespine.com . I have built a bike this past winter using the 26"SUB with upgrades to 700C from xtracycle and plan to do a tour this summer. I hope some of the info helps enjoy your journey.