Some of the concepts for the Double Opt in tutorial will apply, but not exactly.
the link to the users details page will pas the user ID as a query sting, for example:
pass that same query string to the update userlevel page:
<href ="update-users-level.php?ID=<?php echo(isset($_GET['ID'])?$_GET['ID']:""); ?>">Update User Level</a>
on this page, you can create a recordset that queries the users table and filters the ID based on the ID URL variable, it will be the same type of recordset shown on the details page.
using this recordset, you show the existing user level.
add a form with a select list of user levels and a hidden element. the hidden element will use the ID column from the recordset as the value, add another hidden element to use the email column as the value.
you can then add an update record behavior. set the key column to the ID column, set the key value to the ID hidden element.
on the bindings panel, bind the user level to the select list.
then add the universal email behavior. Bind the To Address to the email hidden element.