From first hand expierence you will have some complications that are hidden when uninstalling OXP. I did that once when my Outlook got all mucked up, I restarted, then reinstalled. But somehow OXP remembered exactly how I had my folders and such set up in Outlook and I'm sure it remembers some other stuff about other applications in the office suite. I imagine it plants some stuff in the registry you'd have to remove before you can actually completely uninstall OXP.
But I'm not sure how these remembered things will affect an O97 install, but I'd keep this in mind if your first attempt at installing O97 after Uninstalling OXP fails, before you give up.