There are a number of Word macros which can translate a formatted Word document into MediaWiki markup.  I've no experience with how well they work in Word 2007, and I have no idea if they'll support Hebrew, but they're fairly easy to write and modify, I knocked up something similar for internal use at work a few years back.  They're also fairly limited in what you can achieve.  Not all formatting is easily translated, and not everything on a Wikipedia page can be achieved in Word.  You may face difficulties if you want to continue to use Word for editing once you've posted your article and other people start editing it - in the long run it may be less effort to just learn the Wikipedia markup language.