Awww....really? I haven't got anything but my own experience, and the advice and help from a good shooting friend of nearly 40 years standing who's built several muzzle loaders. But really...I nearly failed shop class in high school. So can it really be that difficult?
I've only built two trade guns; one a Caywood, and the second Track of the Wolf's fusil de chasse. The Caywood taught me how to drill straight holes. (I patched more that a few with toothpicks & stained the stock dark enough you'd have to look for them.) The French gun taught me a bit about locks and how to work over manufacturer's bad designs. The de chasse gun also clued me in on how to inlet French butt plates.
So I learned as I went along. There were bits I messed up...a little. But I figured out how to hide or correct these with a little thought, or the advice of my long time pal. One of the biggest lessons I learned is when to put the tools down and call it a day. So just do it...without deadlines, without schedules.