I have to say it sounds like you have an excellent strategy.
You wowed them with your resume, experience, and phone interview. Now go do it at the interview.
My only advice would be to be honest, but don't say more than you need to all at once. Once you have fully disclosed your diagnosis with them, let them ask the questions, even encourage them to ask them, but maybe don't offer up too much extra information that first day. My only concern would be getting into that situation, everything is going along fine, they are receptive, and then I start blabbering on about how happy that they are willing to work with me, and even though you will have to jump through hoops for me, I will be the most loyal employee. And then they start asking, "hoops, what hoops?" Like Stephanie pointed out, simply make it clear that there is no risk, no downside to hiring you, and leave it at that. You are a valuable human resource, and the more ordinary your situation seems to them, the more ordinary they will receive it. I haven't read over the wiki article mentioned in a while, but if I remember correctly, there is a lot of information there, that while it is important, might be better left to orientation day, instead of interview day. That is unless they ask before then.
That is my two cents.
As far as I am concerned you are a beautiful rebel activist paving the way for all the girls who will come after you.
Hope that makes sense.
Best of luck Annie. Find your day especially well.