Well, Mecareth, I'm sorry people were antagonistic about your post, but you have to understand that this type of question ("am I ready for XXX?") is first of all simply asked too often, and second of all, and the reason why it can get really frustrating, is the fact that there is one common answer every time this question is asked: "we don't know." We don't know who you are, how you practice, how quickly you learn, and so on. A few sentences about your background hardly helps any.
Let me also say that it's a shame that you've just played those four pieces. You really ought to look into playing at least one piece that everybody and his brother haven't done (and butchered).
And as for your book, well, I don't trust that ends in "Dummies."
To answer your question, don't play the Fantasie-Impromptu. You're new, and you'll probably learn it wrong, and that will hurt you in the long run if you ever decide to come back to it, not to mention it's just attempted far more than it should be. Play some Schumann or Schubert, or give the German composers a rest and dig up some Clementi.