PAM RADIUS LDAP SAMBA what a mess!

Hey,
I have a working Samba Server working as a Domain. It uses LDAP as a backend. So with this I can ‘replicate’ Active Directory. Well now things have changed. Now I have to use our IT department’s Active Directory Database. They have given us a Radius Server for us to authenticate against. I have their information entered into /etc/raddb/server I just don’t know which pam.d/ file to edit or how to edit it. If anyone can help me or lead me to the right direction please let me know!
Thanks.

http://lance.mckendree.edu/~ceneblock/Drawing1.jpg
How the setup needs to be, of course it bounces back if successful