I took GhostBSD18.10.iso for a spin in a (rarely touched) VirtualBox guest for GhostBSD that I created in December 2017. Booted the guest from the .iso, ran GhostBSD Installer from the desktop, stopped myself when the installer required selection of a device (in my case, ada0).
If I proceed beyond the ZFS Configuration screen, then will the installer recognise the existing configuration and offer to import the ghostbsd pool? Or will there come a point where the partition table must be changed?
Incidentally: whilst drafting this post (in the host machine), the guest presented an alert for updates so I quit the installer etc. and proceeded with the Update Manager routine. Not because it's a proper way to proceed with an upgrade, whilst booted from something other than the system to be upgraded (!) … just curious. (Someone who has never upgraded might be misled by the prompt to update, in this context.)