I rolled-back to 12.10 and ticked the “Install NVIDIA drivers” option in Apps. The driver installed successfully and I was able to run nvidia-smi from the TrueNAS shell. I then upgraded to 12.10.02. When I logged back in to TrueNAS post-upgrade, I noticed a new job running called “Installing NVIDIA drivers” and none of my installed apps appeared in the Apps section of the UI. After the job completed, my apps re-appeared.
My Plex instance still doesn’t use the GPU for transcoding and the dropdown in Plex does not display an available GPU, but one problem at a time 
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(I’m sure this is all intended behavior but it may help someone that has the same issue!)
EDIT: ran the commands outlined in this post (I forgot to do this when I rolled-back and re-upgraded) and it’s all working now.