How to exit KDE?
 

How do I get out of KDE and back to command mode? I know I can make a terminal session inside KDE, but is it ok to run Xconfigurator and other text configuration programs like that from within KDE?

Kde have a logout icon in the kicker menu (the K where win has the start button) and it should also have one in the pannel near the clock and in the desktop right click menu. You should always shutdown your X server before you make modifications to it, unless the mod is just an edit of the config then you just need to restart it for the change to take affect.

You can always use the text consoles 1 through 6. Jump to them using <ctrl><alt><Fx> x=1..6 The X-Server will be on console 7.

If you want to shut down your x-server, issue the command init 3 from any text console (you need to be logged in as root)

what do you need it for? if it helps change /etc/inittab file
as root - find something that looks like
#default
init:5: and blah-blah
change 5 to 3 save file. Next time you start linux you'll get a console login prompt from there you can start your X (startx) etc.
Have fun.
P.S. make a back up copy of the /etc/inittab !

to exit x-server/kde you can always use CRL+ALT+BACKSPACE as a short-cut instead of the init 3 runlevel command.