Modify CCK Fields with Drupal hook_form_alter

Here is how to modify a CCK field on a node form in Drupal. In this particular example, the CCK field I am trying to modify is called 'field_news_image' and is inside a CCK Field Group called 'group_image'. The modification hides the field by wrapping a div around the field and setting the div's display to none.

function tf_form_alter(&$form, $form_state, $form_id) {
  switch ($form_id) {
    case "my_form_id":
      // attach our #after_build handler so we can modify cck fields
      $form['#after_build'][] = 'tf_form_after_build';
      break;
  }
}

function tf_form_after_build ($form, &$form_state) {	
  $form['group_image']['field_news_image']['#prefix'] = "<div style='display: none;'>";
  $form['group_image']['field_news_image']['#suffix'] = "</div>";
  return $form;
}

Here is how to modify a CCK file field's description, this has to be in hook_form_after_build:

$form['field_my_cck_filefield'][0]['#description'] .= "My extra description for the field...";