So my long time friend just told me he's trans

I have a friend, I'll call him Nigel. We've had sex before and Is a pretty good friend of mine.
I'm gay, and Until today I thought he was too, he's bisexual now.
So we're walking down the street and we start talking and he talks about how bad he feels for minipulating me into sex with him being older than me and how much he regrets it, but thats a whole other can of worms I really don't wanna dive into and happened a real long time ago. I said that it's ok.

Then he tells me that he's one more thing in the LGBT acronym and told me to guess. I said the most logical thing, Trans, jokingly. And he, now she said "Yes, that's me, I am that." And then we start talking about it and then I start talking about myself and how hopeless it feels looking for a boyfriend, and how him, now her turning me down when she was the only gay guy I knew at the time, really made me lose hope, like, if he wont, then who will? Then She holds my hand while I fumble a bit and says that I'm going to find someone, and comforts me. Of course, She has a boyfriend so I knew it didn't mean anything but, it meant a great deal to me, I was holding someone's hand for the first time, it felt great.

I don't know how to feel about Nigel telling me this. Actually, I do know how to feel, I know exactly how to feel, I've had trans friends before, FTM only though, so this was new to me, but I knew that I love her no matter what, she's my friend. It's just that, I don't know how to support her, or what to do or the extra steps I need to make to make her feel safer around me, I've never dealt with someone who was MTF, it's completely alien to me honestly. Nigel, now Jan, had always been this really rough rugged dudely person to me, so this was really out of left field and I didn't know how to react. I think I may be the first person she's told, too.

 

got it, I'll try my best. Should I treat them as like a new person? Or like the same old but different gender? Its a bit jarring and hard to get used to admittedly, I've known this person for the entirety of my time being with her as, like, a dude. But I'll give it my best shot. Maybe invite her over and give her some makeup or like a rad dress or heels to show my support.