Fountain of Knowledge

I'm seventeen years old and will turn eighteen in August. I've been thinking about sending out pieces to a publisher, and once I get my novel completed, I want to have it professionally edited (if I can afford it ) and then possibly sending it out to a publisher. I've heard a lot of things about writers having agents, but are they really needed? Or are agents just for the more accomplished authors out there that already have published pieces?

Also, does anyone know of any good magazines that publish fiction (preferably short stories), and that would accept submissions from young writers?

All the help is appreciated.

- Sara Ann