I am an engineer, so preface what I say with that.
I started my DIY gunsmithing with lot's of forum reading. Yes, there are lots top quality gunsmiths posting know how on the web. Not every last detail, but they give clues to how they work.
I would suppliment this with reading about gunsmithing. Kuhnhausen manuals are a great place to start.
Then you need to start with projects. You might bed your 308 or take your scope off and work through what it takes to mount it straight with the bore and without any cant angle.
In this process, you will learn some basics. You will also learn that gunsmithing is all about working with what you have.
Building a 1911 is a good skill builder. That is really a good primer on part fitting and gun finishing.