Not sure about the first question but the 2nd question, to make the browser recognize the feedburner version, you need to edit your theme.
Look for a few lines that look like these
Code:
<link rel="alternate" type="application/rss+xml" title="RSS 2.0" href="<?php bloginfo('rss2_url'); ?>" />
Change out the link for the feedburner link.
Alternatively, if you don't want to mess with the template you can install the Feedburner plugin. You can grab it from Feedburner itself or WP plugin database.