Second hand information for this stuff will probably get you into trouble.  I would suggest going to the MS site and looking for Windows 7 upgrade information and looking at frequently asked questions.  It may be that the current multi-langual user interface pack you have will be compatible.

Might help...but, it is in English...hope that isn't a problem. 

LINK

Ahah, found some good info here (http://blogs.zdnet.com/Bott/?p=1128&page=2):

LANGUAGE PACKS Here’s a confusing feature primarily of use for multilingual speakers. Within two weeks of launch, Windows 7 will support 35 languages. Your base installation will use the language you purchase initially (U.S. English for most readers of this article), but any user of any Windows edition including Home Premium can download a Language Interface Pack that allows switching to one of the other supported languages. LIPs translate most of the user interface elements. For Ultimate/Enterprise editions only, you can install Multilingual User Interface (MUI) packs that encompass the entire interface. Apple boasts support out of the box for 18 languages.

So it seems that is will only give a few more interface changes and things of that sort. I think that I can handle saving a lot of money just going Professional instead of Ultimate in this case. I'll still keep my eye on this, but thanks!

EDIT: Actually, by going what is in DrJBHL's link, it seems that it might be a lot more convenient to get Ultimate. Going to read more from that link after lunch.

EDIT: Alright, it seems that I don't exactly need the MUI packs, that the LIP's will work for me in the same way. Thanks for all of the help!