So I came out to my mother today on the ride to see my doctor; I thought it'd be fair to warn her that I was going to ask for a referral to a GP. So she took it well - she asked the "boy in a girl's body" thing as she had before (much earlier; I waved off the question because I wasn't sure how to respond) and I gave her my "well, not exactly..." answer and explained in the simplest way I could manage. I don't think she really gets it, but she's been accepting, at least.
I'll still have to work through physical changes as far as surgeries go, but I can do that throughout the year and ease her into it. ("You don't want your breasts??" - Direct quote; she needs to be eased into it.)
So now I'm planning on how to tell the other members of my family - I might have Mother explain it to them to start and then go from there, mainly to see her understanding of it and what she'd be telling others; but, perhaps that's too pushy and I should do it entirely myself.
But, hey, a step! And now I'm slightly more prepared for school next year...
*Raises glass* Cheers, everyone.