I'd say if you're afab and want an official diagnosis then find a good psychiatrist that has lots of experience w autism specifically w women bc I got labelled borderline and I know that isn't what I have.

I would bring it up by letting your friends know that it's something you've been looking into and explain why you think it might be the case. Often, when people we are close to don't react well to different forms of "coming out", its because they have a specific conception of who you are, and while you've been developing new and changing perceptions of yourself, they haven't been involved in the process so they might feel caught off-guard by something that appears very sudden and different to what they think they know. Introducing the idea with detailed explanation of how it applies to you individually can help them understand it better.