My first question is How can I make the "existing Stylesheet" show up in the CSS Slylessheet Editor so I can modify the Body width of my Web Site?
You shouldn't copy the original stylesheet into your Appearance → Custom Design → CSS editor. Instead, what you should do is look at the original stylesheet as a reference, then write new CSS to make adjustments. The new CSS you write should be added to the Appearance → Custom Design → CSS editor.
Changing the width or the Ocean Mist theme is not an easy task because of how the original theme was designed. I worked on it for a while and came up with one possible way to do it. This example won't match the original exactly, but it's close. Also, it uses CSS3 instead of background images to setup shadows and border radius, and so those parts of the example will only work in modern web browsers. If this is acceptable to you, then try out this example by adding this CSS to your Appearance → Custom Design → CSS editor:
#content {
width: 70%;
}
#sidebar {
width: 30%;
}
#mainpic,
#header .pagetabs,
.title,
div#respond h3,
.post,
#footer {
width: 100%;
}
#page,
#header {
width: 980px;
}
#page {
margin-top: 20px;
background: #e8eef5;
-webkit-box-shadow: -2px 0px 6px rgba(50, 50, 50, 0.25), 2px 0px 6px rgba(50, 50, 50, 0.25);
-moz-box-shadow: -2px 0px 6px rgba(50, 50, 50, 0.25),2px 0px 6px rgba(50, 50, 50, 0.25);
box-shadow: -2px 0px 6px rgba(50, 50, 50, 0.25),2px 0px 6px rgba(50, 50, 50, 0.25);
-webkit-border-bottom-left-radius: 5px;
-webkit-border-bottom-right-radius: 5px;
-moz-border-radius-bottomleft: 5px;
-moz-border-radius-bottomright: 5px;
border-bottom-left-radius: 5px;
border-bottom-right-radius: 5px;
}
#content {
-webkit-box-shadow: 8px 8px 20px rgba(50, 50, 50, 0.10);
-moz-box-shadow: 8px 8px 20px rgba(50, 50, 50, 0.10);
box-shadow: 8px 8px 20px rgba(50, 50, 50, 0.10);
}
#sidebar .title {
width: 100%;
background: #cadfed;
-webkit-box-shadow: inset 20px 0 20px -20px rgba(50, 50, 50, 0.4);
-moz-box-shadow: inset 20px 0 20px -20px rgba(50, 50, 50, 0.4);
box-shadow: inset 20px 0 20px -20px rgba(50, 50, 50, 0.4);
}
#content {
background: #fff;
}
#header {
background: #3e4347;
-webkit-border-top-left-radius: 5px;
-webkit-border-top-right-radius: 5px;
-moz-border-radius-topleft: 5px;
-moz-border-radius-topright: 5px;
border-top-left-radius: 5px;
border-top-right-radius: 5px;
}
#mainpic {
background: url(http://cdvnga.files.wordpress.com/2012/05/cropped-header_05_235.jpg) repeat-x !important;
}
#mainpic,
#content {
margin: 0;
}
#footer {
padding-top: 2em;
padding-bottom: 2em;
background: none;
border-bottom: 0;
margin-bottom: 10px;
}
#footer-top {
display: none;
}
#footer p {
padding: 0;
margin: 0;
}
Note that this CSS overrides the background image set in Appearance → Background because that one is limited to a specific size. You can change out the header image by replacing the url() value in the #mainpic block.