I'm pretty sure you don't need to remove Works in order to install Office - you can have both installed at the same time. Word 2007 should be able to open and save to up to Works 7.0 File Format. But I'd recommend saving your stuff once you've opened them to Word 2003 (.doc) or Word 2007 (.docx) for maximum functionality.

Making a backup of your documents before you open them and convert might not be a bad idea in case you have anything in the Works docs that don't fully convert?

Hope that helps!