It's pretty simple to make a skin You have the following components for each section:
"On" image (when the mouse is hovered over)
"Empty" image (with no buttons, so that you can omit buttons from the screen)
"Down" image (when it's pressed)
.skin definition file (defines how/where the buttons are)
The way the skins work is to take the empty image, and display it. It then checks the .skin file for x,y co-ordinates and h,v values for where you want a button to sit. It then loads that section of the "off" part of that. The "on" and "down" bits are then shown when the mouse is over it or clicking.
Therefore, to change where a button is "active", you change the x,y,h,v values for that function, and it will "move" the button to there.
The best way is to take a look at the existing skin files, and change things from there
If you need any more help, just let us know