if you need to get some info about a logged in users previous orders you can do/add the following as to where required (as of wppizza 2.11.8.14)

/**add and instanciate the class*/
require_once(WPPIZZA_PATH.'classes/wppizza.user.details.inc.php');
$userdetails=new WPPIZZA_USER_DETAILS();
/*set the user id - in this case "1112" */
$userdetails->setUserId(1112);
/***
get details as needed
***/
/*get a total count of all completed orders of this user*/
$ordercount=$userdetails->getUserOrderCount();
/*do something with $ordercount*/
/*get an array of all gateways the user has used when ordering */
$gateways=$userdetails->getUserOrderGateways();
/*do something with $gateways*/
/**get total order value of all orders of this user*/
$total=$userdetails->getUserOrderTotal();
/*do something with $total*/