nodeapi case 'files': ??

Now i have a code like so...

function tutorial_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {
    case 'load':
      return db_fetch_array(db_query('SELECT parent, weight FROM {tutorial} WHERE vid = %d', $node->vid));
      break;
    case 'view':
      if (!$teaser) {
        if (isset($node->parent)) {
          $path = tutorial_location($node);
          // Construct the breadcrumb:
          $node->breadcrumb = array(); // Overwrite the trail with a tutorial trail.
          foreach ($path as $level) {
            $node->breadcrumb[] = array('path' => 'node/'. $level->nid, 'title' =>  $level->title);
          }
          $node->breadcrumb[] = array('path' => 'node/'. $node->nid);

          $node->content['tutorial_navigation'] = array(
            '#value' => theme('tutorial_navigation', $node),
            '#weight' => 100,
          );

          if ($page) {
            menu_set_location($node->breadcrumb);
          }
        }
      }
      break;
    case 'update':
      if (isset($node->parent)) {
        if ($node->revision) {
          db_query("INSERT INTO {tutorial} (nid, vid, parent, weight) VALUES (%d, %d, %d, %d)", $node->nid, $node->vid, $node->parent, $node->weight);
        }
        else {
          db_query("UPDATE {tutorial} SET parent = %d, weight = %d WHERE vid = %d", $node->parent, $node->weight, $node->vid);
        }
      }
      break;
    case 'delete revision':
      db_query('DELETE FROM {tutorial} WHERE vid = %d', $node->vid);
      break;
    case 'delete':
      db_query('DELETE FROM {tutorial} WHERE nid = %d', $node->nid);
      break;
      
          case 'fields':
      return array('nid', 'uid', 'type', 'title', 'teaser', 'body', 'revisions', 'status', 'promote', 'moderate', 'sticky', 'created', 'changed', 'format');
  } 
      
      
  }

The question i have has more to do with this part.

case 'fields':
      return array('nid', 'uid', 'type', 'title', 'teaser', 'body', 'revisions', 'status', 'promote', 'moderate', 'sticky', 'created', 'changed', 'format');

Now i know it returns the array but was the array called and how do i use it to design the node page i want. Rather than the default.