Hi, Megan,
A fiery redhead? Ooh, good luck!
Seriously, I think I would have a coming out letter written, even if I decided not to use it. At least she could read it later on. I would have had some information on gender dysphoria she good read when she was ready. I was going to do all that, but it kinda got pushed out sooner. If you have kids, I would hold off on telling them right away, but not too long. If your wife is supportive, both of you showing a united front will help. Most importantly, be honest. As honest as you can be without totally freaking her out. But don't tell her something you think she wants to her. Consider her feelings, but be honest! Trust will be an issue. From then on any lie she catches you, no matter how small, will be a big deal.
I definitely had the "ruined my life" type comments and anger. About 8 hours after I told her, she went into an anger that last 5 days. There have been a lot of ups and downs. She ended up in the hospital because she couldn't take it.
But it ended up being a good thing. She got therapy and we started marital therapy. She's become very supportive. In fact, I dressed in front of her tonight and we had a very good night.
Things aren't perfect. She still doesn't want me to start hair removal or HRT. There's still a lot of work ahead.
It's not easy, but I can say my coming out lifted a weight from shoulders and it was the best thing I did.
Good luck and hugs. Remember you are not alone. Let me/us know how it goes and feel free to ask more questions.