Well, I understand it, but I inherited the management of this site from someone else, and I do not have that file on my own computer... how would I go about changing it?
I see. You could try disabling the Advanced Layout. The changes that were made don't seem to be very significant, and the CSS would likely be enough to keep the site.
If you head to
Admin > Layout > Advanced Layout Options, you can click the "Revert to Original" button, which will disable the Advanced Layout. Or you can right click the "layout file" link, and choose "Save As..." to download the layout file to your computer to work on.