<?php
$post_id = 17907;
$post = get_post($post_id);
$content = $post->post_content;

// Regex to match joomla links with slug
$content = preg_replace('/index\.php\?option=com_content(?:&amp;|&)view=article(?:&amp;|&)id=\d+;([^&"]+).*?">/', '/fea/$1/">', $content);

wp_update_post(array('ID'=>$post_id, 'post_content'=>$content));
echo "Updated post $post_id\n";
?>