I'd suggest graduate, and take classes at a community college if possible, because it'll be way cheaper. Those credits are all the same, anyway. Get flashcards and books and whatnot, twenty minutes a day, and you'll learn just as well as majoring in it, you just wouldn't have the set schedule. Also, you can buy the textbook and not take the class. There are workbooks you can get at larger bookstores or online. Online newspapers. There are tons of resources.

Edit: I saw above you mentioning raising your GPA. Go for it, then. There's everything right with raising your GPA by doing something you enjoy.