First off before tinkering install Timeshift. See my post here:
Then at the terminal enter:
sudo apt-get install xfce4
Obviously answer with Y to install. After install run
sudo apt-get update
Then restart your machine - go to the cog bottom right of login and select xfce.
Keep us posted!
Just attempting myself - you get option to change display manager - I have kept it at GDM3.