Welcome to JW! Like Michael in the post below, I have also been on the steep learning curve that is self-publishing. My book The Mystery Shopper & The Hot Tub is finally published tomorrow!
I had never even heard of Self Publishing School until I read your post.
Jericho Writers has been an invaluable and I think trustworthy source of information on all things to do with self-publishing - especially their online self publishing course free to members.
However, I will say that learning about marketing the book has been the most difficult part of all. It is an overwhelming minefield of information, which you have to assess as to its professionalism and trustworthiness - there are a lot of cowboys out there. There is a plethora of articles, podcasts, books, videos and courses to read and watch that tell you how to do it. However in the end what I really wanted, was to pay someone to actually do the marketing for me, but I have yet to find anyone. I have paid a publicity agent, but they do a slightly different thing.
It is very tough and extremely time consuming and if you are at all non technical and anti social media like me, then it is nigh on impossible without help.
I wish you luck and would certainly advise becoming a JW member and looking at their self publishing course as a starting point.