I'll look when I have some more time.. However vBulletin has some built in functionality for mailing lists in the Admin Control Panel.
Click on Mail Users, and select the proper group from the drop down list. You can then type in your message or cut and paste it in the email.
You can put the user's username and password in the email and point them to the url (
http://yourdomain.com/register.php?action=requestemail).
I hope this helps.