Is it possible to learn the spells without having to become a witch or warlock....

No, it's not, unless you download the wizard stuff from the Harry Potter project. Obviously, sims can't learn the actual apartment life witch spells, but they do have a wand, a book, caldran, ect.

If you want an easier time becoming a witch or warlock (I know I find it annoying to have to make friends with one, myself) over on modthesims2 there's buyable potions for download that turn your sim into either a good witch/warlock or a bad witch/warlock depending on which one you have 'em drink.

There's also hacks that will block the witchy skin and sparkles as well as remove the witch title. So you can make your sim appear normal but still have all the spells.