Hutch, welcome aboard!
You'll find that the first part of a new project is FREE. or almost, and is the best part for making the other parts work:
Get you some kraft paper, or grocery bags in good shape that you can tape together, and draw out what you want. Track of the Wolf, or Muzzleloader Building Supply have catalogs - tho may be out of print, some one will have one you can borrow, rent, or buy. They have life-size drawings of locks, butt plates, trigger guards, etc., that you can copy or trace.
Then you can draw a full-size whatever firearm you want, to fit YOU, and add in the tracings. Get everything that you want to look the way you want it, long before you start getting the pieces together. Figure trigger pull, off-set or on-set, drop at heel, wrist size and shape, triggers, thimbles, etc.
THEN you can go shopping for stock wood, barrels, locks, and so on. Makes it much more understandable if you figure it out ahead of time.
By building one of Jim Kibler's kits, you've taken a big first step and know that you can handle the wood, metal, and their fit.
And don't ever be afraid to try something for the first time, like shooting with your friends down at Neosho. Every one of them had to try it for the first time too, and I bet every one of them will be glad to lend a hand to a new guy. And you are only a new guy once, so remember the things that you see and learn.