Hi Ductape - I'll jump in and answer here as it looks like DT Devs are having a well deserved holiday
Yes sounds a bit scary but to update it is uninstall old via Joomla installer and then install new.... Data remains intact...
It is an unusual upgrade method (hopefully it'll be simpler in future versions) and the main annoyance with it is that you lose every Joomla menu item you may have configured for DT Reg - You have to re-establish all of those each time you update