Open the skin.css file.

 Look for #wrapper

Change width: 992px; to width: 100%;

I'd also recommend that you use Firefox and firebug for debugging CSS and HTML. With a little practice you'll see how yours and other pages are created using HTML and CSS

I figured this out .  

To change the skin width, open the skin.css file and search for each occurrence of "width"; you'll see the large skin width at 960 if I remember correctly; change all those widths to your new skin width.  Then subtract the difference between your new skin width and the old skin width; mine was 189.  Then go through skin.css and look for the content panels...  you'll have to accommodate for that extra width in the content panes.  I did it by increasing the center width in the 3 column and modified other panes in the others.

Next if your skin is over 960 you'll have to widem the image file named "Header-BG-Variable.png" in the skin root folder.  That image is the background for where the menu sits.  It's 960 pixels wide; modify the width only (non-proportionate width change is fine) to be your new skin width.

Then you will be able to sleep that night.