Exit menu - modify?

Is there a way to modify (edit out) the exit menu items?

yes, you can modify DialogButtonMenu.xml
it's in the 720p folder of the skin you"re using.

just keep mind any modifications will be wiped when the skin is updated.

Thanks.

is there a wiki link which would help me understand the format?

there's an entire section devoted to skinning on our wiki:
http://wiki.xbmc.org/index.php?title=Skinning_Manual

that being said, the best way to get started is just look at the code,
try to somewhat understand the structure, make a few changes and check what happens on-screen.

Thanks.