Hmm well, it's kinda hard to explian you this.
I strongly reccomend you to read the article about transexuality on the english version of wikipedia (search on that website, looks like I can't post the link) it contains a LOT of useful information
And you've got to think about this seriously. Remember that if you take this decision, your life is going to change, on a good way or a bad way, and that will depend on you.
I was goign to do the same, but I had a lot of problems and decided to give up. Here in Mexico, there aren't many chances for transgendered girls. Seriously think about it, carefully, take your time, and don't push yourself until you're completely sure that you want this okay?
and u got our support (or at least mine lol)