Q:

How do I retrieve menu items from one level only?

The WordPress function wp_get_nav_menu_items returns my whole site's navigation nested and all. Now if i want to get the nav menu for one "level" of that nested navigation only, how do I do that?

A:

If you want to return an array of items (not output like wp_nav_menu), you can try this:
$menu_name = 'your_menu_location';
if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $menu_name ] ) ) {
    $menu = wp_get_nav_menu_object( $locations[ $menu_name ] );

    $menu_items = wp_get_nav_menu_items($menu->term_id);

    foreach ( (array) $menu_items as $key => $menu_item ) {
        if ($menu_item->menu_item_parent != 0 ) continue;
        $title = $menu_item->title;
        $url = $menu_item->url;

        DO WHAT EVER YOU WANT HERE 

    }
}   // endif has nav menu or not

A:

Are you trying to display the posts from the top down a certain number of levels?
If so, use wp_nav_menu. It has an argument "depth" built just for this and it works painelssly.
wp_nav_menu(array('depth' => 2));

Also, http://codex.wordpress.org/Function_Reference/wp_nav_menu

