My daughter came home from school and told me she's a boy.

I'm still in shock over this. My daughter is 12 years old. She's always been a girly-girl. Flaming heterosexual and always dresses like a Barbie doll. I never would have expected something like this. She told me a few days ago she is actually a boy and wants to live as a boy from now on. I asked if this is a permanent thing or just a phase and she said permanent. She also said she wants to get top surgery and a gender change surgery and he wants to change his name. She told me she's always felt like a boy inside a girls body and said she has been feeling this way for five years. I told her this is a lot to take in but I'll support her and said we'll figure this out. A few days have passed and I still don't know how to feel about this. She said she wants to tell her friends at school tomorrow and said she wants to stop identifying as a girl and start identifying as a boy. I told her I'll support her but I just need a minute to process all of this. Did this happen to anyone else here? How did you handle it? I would massively appreciate any advice.