Ditto what Matt said - install over the top. One other advantage to that is that BIAB will pickup your settings from the previous version (e.g. file locations) so you don't have to redo all of your custom program settings every time. I have never had to revert to the earlier version (builds is a different story) so that shouldn't be an issue. And the new RT setting to get rid of the bloat works great.
Good luck.