I think you might need another installation of WordPress for this… Who owns that page? You need to install a a fresh install, copy the files and text and content over then (you should have to sites that are the same) go to the one that you’re going to put in the frame (duplicated version) and go to the editor.
You should be able to edit the index.php
file, the single.php
file, the page-template.php
file and basicly all the files that have the tags <?php get_footer(); ?>
and
<?php get_sidebar(); ?>
Im not too sure about the header though….