Ability to string replace a returned data guestbook_info

How to string replace a returned data guestbook_info

for example, in the following code ( gb module, drupal )

function _guestbook_info($uid, $data) {
  global $user;
  static $info;
  $guestbook_mode = variable_get('guestbook_mode', GUESTBOOK_SITE_GUESTBOOK | GUESTBOOK_USER_GUESTBOOKS);
  
  if (!isset($info[$uid])) {
    if ($uid == 0 && ($guestbook_mode & GUESTBOOK_SITE_GUESTBOOK)) {
      $info[$uid]['title'] = variable_get('guestbook_site_title', t('site guestbook'));
      $info[$uid]['intro'] = variable_get('guestbook_site_intro', '');
    }
    else if ($guestbook_mode & GUESTBOOK_USER_GUESTBOOKS) {
      $guestbook_user = ($uid != $user->uid) ? user_load(array('uid' => $uid, 'status' => 1)) : $user;
      if ($guestbook_user->uid && $guestbook_user->guestbook_status == 0) {
        $info[$uid]['title'] = t("%name's guestbook", array('%name' => $guestbook_user->name));
        $info[$uid]['intro'] = $guestbook_user->guestbook_intro;
      }
    }
  }
  return $info[$uid][$data];
}

if I want to change :) to a gif in the html output in browser fromreturn $info[$uid][$data];
where in the above code do I get to do that ?

I tried something like
$data = str_replace("[:--)","", $data);
but, errr .............................. that does not work :-(