I think the answer may depend a little on where you are coming from. Are you new to this sort of rifle, or are you an experienced user with one or more very nice examples on hand? If you don't have experience or have a nice rifle as an example, it is a good idea to go to a show and look at and handle some. Are you close enough that you can go to Dixon's in a few months? There are usually good shows every few months in the East. I don't know about other areas. Ask a lots of questions. People will talk your ear off with details! Getting good rifles in hand helps well beyond just seeing pictures. Then you'll appreciate some of the differences between a rifle and a GOOD rifle as you'll have had both in your hands. Then you might have a better idea where on the spectrum you want to focus.
That's assuming you don't already know.
You know, there are a couple video threads on this forum that might be a good place to start.
Perhaps first would be Jim Kibler's colonial rifle build thread. Not that this is how it goes when you make your own, but you see the sequence of how the assembly part goes together and how it should look when going together when everything is going right (yeah, doesn't always work like that).
Then there are some build threads where people made rifles from planks and documented through videos.
After that, where you have SEEN the process in action, and handled good examples, the books such as those already recommended are quite useful.
Lots of your questions on tools and usage can be answered by going through threads in this forum.
If you are on the fence about whether this is the sort of thing you want to do, I'll suggest considering a Kibler kit. You'll have to do minor touch-up inletting, Metal cleanup and polishing, lock tuning, finishing wood, that sort of thing. Carving and decorative inletting and engraving, if you have the skills and are so inclined. But the major architectural decisions are all made and well made at that. A good choice of components is already selected and provided. The resulting rifles (SMR or Colonial) are very nice guns. When you are done you have something nice to show, nice to shoot, and a nice example of a well architected rifle. Having a nice rifle on hand is good when building another!
After that, precarves, planks, up to you. You'll have had more hands-on experience and have acquired at least a necessary set of tools for good portions of the process.
You can get some "plans" that show the architecture. The quality varies, as does the price. I collect them when I find them, along with good quality books. Documentation on the rifles helps a great deal. It is the little details which distinguish schools, makers, and for that matter, good rifles from not so good.
That's not the answer you are looking for, but it might be a direction worth considering if you are not certain of what you want to do. Building from scratch is a LOT of work! I haven't built from a plank yet but I have inlet barrels of different shape/width into existing inlet, locks that are different than the original precarve, altered the overall architecture, ... I have a couple planks on hand, but the gunstocking bench isn't completed yet.
Gerald