This should do what you’re looking for (adapted from the link idowens mentioned by the Woo founder).
<?php
$tag = $wpdb->get_var($wpdb->prepare("SELECT term_ID FROM $wpdb->terms WHERE name='Long'"));
$args = array(
'showposts' => 1,
'tag' => 'Quote',
'tag__not_in' => array($tag),
'orderby' => 'rand'
);
query_posts($args);
if (have_posts()) : while (have_posts()) : the_post();
echo the_content();
endwhile; endif;
wp_reset_query();
?>
