Microsoft Office, I believe, comes with an uninstaller. I'd recommend running that instead of the uninstall method I'm about to suggest...
While this could very well incite a Delicious Generation-related riot, I really like apps like AppZapper, AppDelete or CleanApp for uninstalling programs. True, you don't TECHNICALLY need them, but for whatever reason, I just feel better after clearing out the preference files and caches apps leave behind.
These apps have simple drag-and-drop interfaces and couldn't be any easier to use.
To really save the space here, you'll need to delete GB's effects loops. I typically get rid of these by re-installing the OS first thing and just unchecking all the stuff I don't want (language translations, iDVD themes, GarageBand and its loops, etc).