First thing to do is get a copy of notepad++.
http://notepad-plus-plus.org/
Next is to uncompress all the files in the ePub except META-INF and mimetype.
If you need to change the extension from .ePub to .zip, that's OK. You can rename it later when you want to test it.
In the uncompressed OEBPS directory delete the file page-template.xpgt. You don't need it and you don't want it.
Load all the .html files into notepad++. They will load in separate tabs.
In one of the HTML files select the line that is...
<link href="page-template.xpgt" rel="stylesheet" type="application/vnd.adobe-page-template+xml"/>
Then hit control-h and you will see the search/replace dialog. The line you selected should be in the find what line of the dialog. Now make sure the Replace with line is empty. Check Wrap Around and Normal. Then click Replace All in All Opened Documents. That will do the search/replace among all the HTML files in all the tabs in one go.
Then do the same thing for the line that shows...
<meta name="Adept.resource" value="urn:uuid:b335f548-71c6-4cc5-b736-2065f32554f3"/>
Then go to the file menu and select Save All.
Next, load the OPF file (jaguarprincethe.opf)
Delete the line that shows...
<item href="page-template.xpgt" id="pt" media-type="application/vnd.adobe.page-template+xml"/>
That gets rid of the page-template file from the OPF file.
With Notepad++, you may be able to right click on the selected files in Windows Explorer and select edit with Notepad++. That will load all the selected files in one go.
After you've edited the OPF file save it and then go to the file menu and select Close All.
That's the first step to sorting out the files before beginning to edit the CSS.