If you are just wanting to modify the actual content.

<?php
/*
Template Name: Custom Template
*
*/
?>
<?php remove_action( 'genesis_post_content', 'genesis_do_post_content' ); // Remove genesis content function ?>
<?php add_action( 'genesis_post_content', 'custom_do_content' ); // Add custom content function ?>
<?php function custom_do_content() { ?>
<?php the_content(); ?>
<?php } ?>
<?php genesis(); ?>