Just to add to this. You don’t need to go through the clean Debian steps.
All you need is a v3 Firmware. I’d already updated so I followed this guide: http://community.wd.com/t5/WD-My-Cloud/GUIDE-How-To-Unbrick-your-2TB-3TB-4TB-My-Cloud/td-p/765959 to go back to v3.
Then follow the bitbucket guide. I had to add contrib and non-free to the /etc/apt/source.list to install debootstrap.
Once the chroot is setup, add libexpat1 (apt-get install libexpat1)
Once you have Plex installed, in the WD UI, turn off DNLA media sharing and add the shares you want to share through plex (ie TV, FILMS, 3D) then add them to the /etc/fstab in addition to those described in the guide:
/home /DataVolume/chroots/wheezy-armel/home none bind 0 0
/mnt /DataVolume/chroots/wheezy-armel/mnt none bind 0 0
/tmp /DataVolume/chroots/wheezy-armel/tmp none bind 0 0
/proc /DataVolume/chroots/wheezy-armel/proc proc defaults 0 0
/dev /DataVolume/chroots/wheezy-armel/dev none bind 0 0
/dev/pts /DataVolume/chroots/wheezy-armel/dev/pts none bind 0 0
/nfs/Movies /DataVolume/chroots/wheezy-armel/movies none bind 0 0
/nfs/TV /DataVolume/chroots/wheezy-armel/TV none bind 0 0
/nfs/3D_Movies /DataVolume/chroots/wheezy-armel/3D_Movies none bind 0 0
where /DataVolume is my version of /data in the guide…
The bottom 3 rows are my Datashares. Then in plex I add a Movies share and use “/movies” as the directory.
Another change I had to make was change LC_ALL=C in the startup script. I’m not sure why but the US locale didn’t work for me.