Use the instructions here to perform an uninstall:
To install Plex Media Server on Raspbian, download the ARMv7 package from: https://www.plex.tv/media-server-downloads/#plex-media-server
Then run sudo dpkg -i plexmediaserver-version.deb, replacing “plexmediaserver-version.deb” with the name of the file you downloaded. This will install Plex Media Server and add the appropriate repository.
If you’d like to change the user under which PMS runs, use the instructions I linked above. It shows an example of how to change the user. Per the post, all customizations are made to /etc/systemd/system/plexmediaserver.service.d/override.conf, on a systemd-based system (which Raspbian is).
After doing all that, you can add the mount(s) as described in the post you linked above. When you issue the commands to install NTFS support, use the install operation:
sudo apt install ntfs-3g
