Wow! Sounds great! Keep us updated, please!
As for giving her your contact info, I'm not sure about that... I personally wouldn't do it. I don't think that that could come off in a way that doesn't make you look desperate for her attention, or stalkerish, or like a crazy fan. Maybe if you came up with a fun way of doing it, like... "If you can read this, send me an e-mail

" in English with some custom smiley-face and your e-mail address. But then again, that might be a terrible idea. In any case, if you can make someone laugh they'll instantly like you more, so I'd definitely try to think of something funny. Now, I haven't been to any signings myself, of course, so feel free to disregard everything that I just said. It could be common for fans to give the actress their contact info for all I know!
EDIT: All right, I just took a quick glance at her twitter and blog. It looks like she's recording an album or something, so if that's the case, you could wish her luck with that and write something along the lines of "I hope to see you at your CD signing next". Also, she's got some pictures up on her blog where she's with a cat - I'm assuming with one that she owns, so if you can draw a smiling cat face as a smiley, that would be preferable I think. Even if it's not hers, most girls love cats for some reason, so I doubt that you could go wrong with that. Besides, it's Japan, so probably everyone loves those cutesy cat smileys there. Probably.