If you were to take a writing class, I'd take only one, such a class dealing with how to structure a novel. Or read Stephen King's book "On Writing," which is phenomenal. Then yeah, just let it rip.

Regarding publishing, it depends what you are looking for. Some self-published authors have a bigger following and make more money than traditionally published authors. But you have to do all the self-promotion and build a large audience on social media. You would still have to promote if traitionally published, but not to the degree that a self-published author would. And then of course there is the esteem of being a traditionally published novelist.

If you have the time to devote to writing a novel, I'd just start chipping away. Nobody says you have to write for eight hours a day to complete a novel. It can take you however long you want and be whatever your schedule allows. All of this might seem fairly obvious, but just wanted to share. Good luck.