php code help please

Below are two scripts from a joomla module. The first calls in the gamertag from a parameters field in the back end of joomla and the second is the php for the module. Hopefully a very simple answer for this,
I have created a new field on the register page for the gamertag and this is stored in a database (jos_users)(gamertag)this part works fine, how do i change the script so it gets the gamer tag from the database

Many thanks


<?php
/**
* @version $Id: helper.php 4330 2006-07-26 06:24:14Z webImagery $
* @package Joomla_1.0.0
* @copyright Copyright (C) 2005 - 2006 Open Source Matters. All rights reserved.
* @license GNU/GPL, see LICENSE.php
* Joomla! is free software. This version may have been modified pursuant
* to the GNU General Public License, and as distributed it includes or
* is derivative of works licensed under the GNU General Public License or
* other free or open source software licenses.
* See COPYRIGHT.php for copyright notices and details.
*/

// no direct access
defined('_JEXEC') or die('Restricted access');

class modgamercardHelper
{
function getParams(&$params)
{
$params->def('gamertag', '');
return $params;
}


}



















<?php
/**
* mod_gamercard is free software. This version may have been modified pursuant
* to the GNU General Public License, and as distributed it includes or
* is derivative of works licensed under the GNU General Public License or
* other free or open source software licenses.
*/

// no direct access
defined('_JEXEC') or die('Restricted access');

// Include the syndicate functions only once
require_once (dirname(__FILE__).DS.'helper.php');

$params = modgamercardHelper::getParams($params);

$gamertag = $params->get( 'gamertag');
$class = $params->get( 'moduleclass_sfx' );


$targetURL = "http://gamercard.xbox.com/" . urlencode($gamertag) . ".card";

?>

<div class="gamercard<?php echo $class ?>">
<IFRAME src="<?php echo $targetURL ?>" scrolling="no" frameBorder="0"></IFRAME>
</div>