First off, you might think about getting another SD-card that is identical to the card you have. Put the current card up somewhere and use the new card for a new build. After you get something that works, the second card can be used as a clone for OS backup using this -> process.
If it turns out that the preinstall Script wasn't used and I'm forced to a reinstall, what would be the best way to perform it?
Do a standard R-PI install as outlined in the -> R-PI document which includes the preinstall script That does mean the loss of all current configuration but that's the fix. (Again, this time around, clone the SD-card once it's configured and working. With a clone, you'll have a quick recovery option in the future.)
To keep my settings, I should most likely start with the OMV-regen command to backup my settings in advance, omitting the Network interface settings, as proposed by chente. Where will this backup be stored?
I don't know what to tell you here. I've always done clean installs, then reconfigured from scratch. (While that can be labor intensive - I believe scratch rebuilds help to keep admin's familiar with the configuration processes required by the GUI.)
In the bottom line, I haven't used OMV-regen. If you want to use it, the best thing to do would be read over the -> OMV-regen document and look through the questions thread at the end. Additional questions from there would be best directed to chente.
One difficulty that I can foresee is that the R-PI must be on the network to download the script. At this point, that's probably not possible. (Keep in mind that I'm speculating on what "might" have happened, based on what you described in your first post. We won't know for sure until the wired int name is confirmed.)
Assuming that networking is out, I suppose the OMV-regen script could be downloaded to another host and placed at the root of the R-PI's SD-card, using a file-manager. Then it could be executed on the R-PI using the cable for a CLI console connection as root (or, in the case of the R-PI, as sudo).