Great motion in the nebula! And and a nice vivid (ahh!) mixture to the stars! Overall nice composition! The only thing I don't think particularly much of is the textures of the planet and the moons. They're not bad... but... you know, not interesting. Anyway, still love the background!
Nope. But there are tons of the all over the net - just use google + photoshop space art tutorial - the best for beginners. Advanced tutorials are not necessary since after that it's all about practice and patience.