3. reboot and you will be using KDE Also, at login select KDE from menu. Adjust login selection so that KDE is default.
4. the KDE menu (traditional-select from widgets) will have a Gnome subsection which will have various useful Gnome apps that will run in KDE. Rhythmbox is a favorite. I also prefer the Gnome system monitor.
I dropped GDM due to the lack of a login manager and the root login BS.