Multisite, either change the name of sample-page or create new page

Core function

The core function wp_insert_post() can add & create posts (of every post type).

Plugin

/*
Plugin Name: Add default blog pages
Plugin URl: http://goo.gl/5e1DC
Author: Kaiser
Author URI: http://unserkaiser.com 
 */
/**
 * Default Blog pages - used to define all default pages.
 * Adjust this to your needs:
 * For a full example of what you can define for every page, take a look at
 * @link http://codex.wordpress.org/Function_Reference/wp_insert_post
 * @return array
 */
function wpse50318_default_blog_pages()
{
    return array( 
        array(
            'post_title' => 'About'
        ),
        array(
            'post_title' => 'Contact'
        )
    );
}
/**
 * Adds Default Blog pages
 * @return void
 */
function wpse50318_add_default_pages_to_blog()
{

    foreach ( get_pages() as $page )
        $existing_pages[] = $page->post_title;

    // Get only non existing pages:
    $new_pages = array_diff( $GLOBALS['$wpse50318_default_blog_pages'], $existing_pages);

    // Loop over the non existing & add them
    foreach( $new_pages as $page )
    {
        // Create post object
        $page['post_status']  = 'publish';
        $page['post_type']    = 'page';

        // Insert the post into the database
        wp_insert_post( $page );
    }
}
add_action( 'activate_blog', 'wpse50318_add_default_pages_to_blog' );