[chicgeek]

Easy way out.

Find this at the top of your template.

 #header {
    background:#476 url("http://www.blogblog.com/rounders4/bg_hdr_bot.jpg") no-repeat left bottom;
    margin:0 0 0;
    padding:0 0 8px;
    color:#fff;
    }

Create image. 740px wide by 150px tall.
Upload somewhere.
Change the image URL in your code above to the new location.