is simple,if you have GNOME and want also KDE, install KDE-META with equo or directly in Sulfur. You may also add many KDE aplicatives....
after, when you login, you may choose KDE or GNOME.
I have, and also many other graphical ambients...
ALBERTO FEDERMAN NETO
Favorite Distros: Sabayon, Gentoo, Mageia and OpenSUSE