It should upgrade without issue. I do, however, always recommend that you backup a copy of your database prior to doing any type of upgrade to your site.
Also, prior to upgrading to Garage Plus, make sure you walk through the steps in the documentation. One of the steps includes installing a permissions product file since Garage does not honor any type of permissions related to the number of garages per usergroup. All of this and more is included in our online documentation. You can see the 2.0.0 Garage Plus documentation
here.
Thanks!
Mark