There are three snippets for FedEx. If you cannot use the dynamic selection then use the correct code for the field in the checkout wizard. For any of these that you use you must ensure that you use that snippet on the checkout page.
Service Type:
<?php echo((isset($_POST["FedEx_Service"]))?$_POST["FedEx_Service"]:"") ?>
Carrier:
<?php echo((isset($_POST["FedEx_Carrier"]))?$_POST["FedEx_Carrier"]:"") ?>
Package Type:
<?php echo((isset($_POST["FedEx_PackageType"]))?$_POST["FedEx_PackageType"]:"") ?>
After you insert the snippet for the service type you will need to ensure that you add a hidden form element with the same name to the confirm page and set the value to this same element.