[nijiro]

Go out and buy a Beginner's Japanese language book. Your girlfriend will think it's sweet and it will help you a lot more than anyone on here can. You can get a nice one like Teach Yourself Beginner's Japanese for about ten bucks. There are also a few cool sites that could be helpful, for example, YesJapan, but they charge you monthly to use their lessons (they're really good though!). Don't trust another person to teach you from the ground up unless they are an actual Japanese professor. Books, books, books! Programs are alright, but I have yet to find a really good, comprehensive one (besides Rosetta Stone which is hundreds of dollars).

As for typing, you need to have a certain program installed in order to type Japanese characters. If you're using Windows, that means you need Microsoft IME. Vista comes pre-packaged with it, but if you have an older operating system, you'll have to Google it to find out where to download the program and how to install it properly.
But for your purposes, you can generally be understood by typing in Romaji or romanized Japanese. (for example, watashi wa igirisujin desu "I'm British") I'd say do some studying before you start trying to type in Japanese... after all, if you can't read it, how can you write it?

If you have any other specific questions, I'd be glad to help.

Ganbatte - Good luck!