Janine, if you haven’t written a screenplay before, I would recommend you write the novel. After you’ve rewritten it and gotten it into best shape possible, you can submit to publishers. If you do have an interest in adapting it as a screenplay, there’s no reason you can’t study the craft and take a whack at it. If only there were a free online resource with over 25,000 articles on the craft of screenwriting. Wait! There is! Go Into The Story!
Good luck with the writing!