Thanks for the guidance. I added the $_SCRIPTS->setJavaScriptLibrary('jquery'
; to the function.inc and the code below to my index.php. All appears to be in order.
Text Formatted Code
// MAIN
global $_SCRIPTS;
$_SCRIPTS->setCSSFile('storygallery', '/storygallery/style.css', false);
$_SCRIPTS->setJavaScriptFile('storygallery', '/storygallery/jquery.tablesorter.min.js');
$js = "\n" . '$(document).ready(function()' . "\n";
$js .= '{' . "\n";
$js .= ' $("#storygallery").tablesorter( {sortList: [[0,0], [1,0]]} );' . "\n";
$js .= '}' . "\n";
$js .= ');' . "\n";
$_SCRIPTS->setJavaScript($js, true);
$display .= COM_siteHeader('menu', $LANG_STORYGALLERY_1['plugin_name']);