!GET OUT!
Naw, just kidding around. Welcome! I'm relatively new around here, as well. My wife just left me last week, but we're still on relatively good terms, considering. Not all relationships are doomed just because they include a TS partner. I really suggest picking up "Head Over Heels: Women Who Stay with Crossdressers and Transsexuals" and reading through it. It will give you a lot of insight into what your partner might go through, and how best to come out to her.
Also, "She's Not There", by Jennifer Finney Boylan is a nice book-length personal essay written by a woman who transitioned while she was not too much younger than you. While it won't give you the wide view that Head Over Heels will, it's written from the perspective of the TS partner and is very readable.