Sorry to burst your bubble here sir, but you will most definitely have to uninstall the Beta before you can install the RTM version of Office 2010.
I may be wrong here, but I think during the uninstall process it asks if you want to keep the settings, I can't remember because it's been a few months for me.
I know it's a P.I.T.A.! However, it's necessary in order to install the full retail version.
Just grab a can of pop or a cold beer and relax and before ya know it, you'll be all setup and back the way you were.
~ Nibs