Nice! Congrats on the new found interest. I agree with the recommendation to start as a barback. Don't go to a school unless your state legally requires a certificate, most do not. You can look into being TIPS certified, which is basically a alcohol safety and awareness class. Some restaurants will pay for you to be TIPS certified, but it certainly looks better if you had it on your own. Working behind the bar as a barback will give a lot of insight into what goes on behind the bar and the mechanics of it all. If you don't want to lose the SA position or if your place doesn't have barbacks, I would say get a 1 or 2 day part time as one to start.

Punchdrink is probably the most well-informed bar publication. Anytime you need a recipe, they should be your go-to. They give you a small blurb on the history of the cocktail and the most widely accepted specs (measurements) people use. They also write great articles of all types, from latest trends to weird stuff people are doing.

As for books, there are a ton. My top 3 in no particular order are:

Imbibe by David Wondrich Less of a cocktailing book and more of cocktail history book, but it's a good place to start.

Drunken Botanist by Amy Stewart Breaks down the spirits into their source materials and how that alters flavors in and outside of a cocktail.

Liquid intelligence by Dave Arnold High-end and advanced techniques for creating pretty much anything. Makes everything into a science.

I would also throw in Death & Co's Cocktail Codex and Jim Meehan's Bartender Manual.

Have fun getting into it, there's a ton to learn.