Load scripts in the footer of your site. The preferred method for WordPress would be to register and enqueue your javascript, but this will work at least for proof of concept.

load-script-to-footer.php

<?php
/**
 * Load scripts in the footer of your site. The preferred method for WordPress would be to register and enqueue your javascript, but
 * this will work at least for proof of concept.
 */
function load_script_to_footer() {
    if ( is_page( 'membership-checkout' ) && '1' == $_REQUEST['level'] ) {
?>
    <script>
        // load your script code here.
    </script>
<?php
    }
}
add_action( 'wp_footer', 'load_script_to_footer' );