Hawkens are right up my ally, and yes, they are difficult to build. More mechanical and precise measurements than a solid breeched, pinned, fullstock, flintlock.
Like mentioned already, I recommend a simpler kit gun, or even a simple trade or plains rifle for your first build. No exacting lines to follow. However it turns out is still P/C. You can pin the barrel and use a solid breech, and use whatever stock shape you want.
But, if you have your heart set on a genuine Hawken, and want to use maple, I do recommend starting with plain maple, instead of a fancier grade. Curly maple is trickier to work with, along with the added difficulty of copying the Hawken features. And if you mess up a little, you aren't out much money. Plain maple is actually more correct for a Hawken.
I buy the bulk of my parts from Track of the Wolf, and make many myself. The wood comes from Dunlap Wood. Lately, I've been getting GM barrels from Muzzleloader Builders Supply, but call first, since that guy doesn't update his stock very often. And the girl who works there likes to flirt. :grin:
Good luck. Ask questions as you go. Bill