I have GDB v1.0, does the device need to be connected to the router all the time?
For GDB v1.0, yes. It needs to be connected to the router via an ethernet cable all the time.
installation
Will existing remotes still operate as normal?
Yes, make sure you don’t hold the learn button when you program GarageDoorBuddy to your opener. Holding the learn button will erase the opener’s existing remotes.