THis is not exactly what I need. I did some hack in the file businessdirectory-excerpt.tpl.php, now the code is like this:
<?php echo $thumbnail; ?>
echo substr($listing_fields,0, 1000) . "...";
This will display only the first 1000 characters of each listing on the Listings Page.
That part is ok, what I need now is to edit the single listing page. I don't seem to find out how to edit just the content part, I mean, there is a function called $listing_fields in the file businessdirectory-listing.tpl.php, it displays the full listing, I need to know how to display just the description, how can I do that? I tried:
echo $listing_fields .= $field->display( $post->ID, 'excerpt' );
echo $listing_fields .= $field->display( $post->ID, 'listing' );
But it didn't work.