Well, the easiest way, is to make a new template with your content in (ie postbit_gallery) then in functions.php
find
PHP Code:
eval("\$post[buddy] = \"".gettemplate("postbit_buddy")."\";");
underneath add:
PHP Code:
eval("\$post[gallery] = \"".gettemplate('postbit_gallery')."\";");
then find
PHP Code:
$templatesused = 'postbit_search,postbit_buddy,postbit_useremail,icq,aim,yahoo,postbit_homepage,postbit_profile,postbit_ip_show,postbit_ip_hidden,postbit,postbit_sendpm,postbit_avatar,postbit_offline,postbit_online,postbit_editedby,postbit_signature,postbit_attachment,postbit_attachmentimage,showpost';
and simply add ,postbit_gallery after showpost
Then in your postbit template, add $post[gallery] anywhere you want