can I change it now to something I would like to call it? Would this cause any problems? Would I have to modify any files to tell it the admin file named changed?
Not if you are using ZenCart 1.5.1 and the admin configure.php file that came with it
Download that file open it in a code editor and at about line 33 you should see this "preg_replace"
Code:
$t1 = parse_url(HTTP_SERVER);$p1 = $t1['path'];$t2 = parse_url(HTTPS_SERVER);$p2 = $t2['path'];
define('DIR_WS_ADMIN', preg_replace('#^' . str_replace('-', '\-', $p1) . '#', '', dirname($_SERVER['SCRIPT_NAME'])) . '/');
define('DIR_WS_CATALOG', '/');
define('DIR_WS_HTTPS_ADMIN', preg_replace('#^' . str_replace('-', '\-', $p2) . '#', '', dirname($_SERVER['SCRIPT_NAME'])) . '/');
define('DIR_WS_HTTPS_CATALOG', '/');