If you use the command: yum groupinstall "X Window Server" "GNOME Desktop Environment" it will take care of your needs for right now. If you use the "man yum" command, the man page will give you a list of the variables that can be passed to the yum command. If you are especially daring you can run "man rpm" and try to use rpm to do the same thing.
Remember, "man" pages are your best friend.
Let me know how everything goes..
D