As page ovrride view will simply stop the content of the pages from viewing. Now to change content of the page you need to use this hook.

<?php
function override_group_page(){	
	ossn_add_hook('page', 'load', 'new_group_page');
}
function new_group_page($hook, $type, $return, $params){
	if(isset($params['handler']) && !empty($params['handler']) && $params['handler'] == 'group' && $params['page'][1] == 'edit'){		
		$id = $params['page'][0];
		echo 'new stuff';
	}
}	
ossn_register_callback('ossn', 'init', 'override_group_page');

You need to use this in combination of https://www.opensource-socialnetwork.org/documentation/view/5583/page-override-view