All what's on the screen is written in files, store in: 

Information files: /usr/lib/enigma2/python/

Graphic files: /usr/share/enigma2/

Font: /usr/share/fonts/

It all is managed by /usr/share/enigma2/you_skin_name/skin.xml

To not damage: don't work with Information files

The Information files are just to look at while making skin. 

If something goes wrong, and you can't find your bug

you can change skin in /etc/enigma2/setting