When is prom, like March or April? Seriously I think it's a bit soon. Maybe it's just me... I mean I asked around the end of February, and she said it was pretty much perfect timing, gave plenty of time to find a dress and whatnot (prom was mid-April). I understand wanting to get everything in order, but half a year for prom is a bit... exorbitant. In my opinion, anyway.
As for the rest of what you asked, I would definitely try to do it in person. And there's no shame in asking someone from outside of your school, plenty of people at my school did it (or went to proms at other schools).
-------
Ein heißer Schrei... Feuer frei!!!