The garage integrates in a pretty seemless way, I would not expect any updates to phpBB3.0 to require any work to keep the Garage working. If a version does require changes then I will support it ASAP and a new version will be produced. However you would not need to reinstall just make whatever changes are needed to keep it working.
Remeber all the data sits in its own tables and 99% of files are 100% garage related. So only places we integrate are profile, topics & header, and even there the integration is neatly done.
The beta should have been ready today
but when the converter ran on my live site it went nuts so working to fix that ASAP.