How can i change the templating of a form in sfDoctrineGuardPlugin?

That is, I need to change the html (class, id) of the input elements (username, password) of a login form provided by sfDoctrineGuardPlugin.

I've changed apps/app_name/modules/sfGuardAuth/templates/singinSuccess.php, but it then just echoes $form (I need to change contents of that part - $form):

  <form action="<?php echo url_for('@sf_guard_signin') ?>" method="post">
    <table>
       <?php echo $form ?>
    </table>
    <input type="submit" class="go_button" value="ir" />
    <a href="<?php echo url_for('@sf_guard_password') ?>"><?php echo __('Forgot your password?') ?></a>
  </form>

(It really should be something like changing a _form.php => I cant find this, though :S)

Thank you all for any answers provided =)