Thanks to Derek Solaris for doing all the work on this and letting me post it in my blog!
As always, make sure you have a current backup of your Active Directory before attempting this procedure.
Utilize ADModify to perform bulk update of user's Display Name to the format of Last Name, First Name.
Process to perform this:
Download ADModify from: http://admodify.codeplex.com/
Extract ADModify binaries from the ZIP file.
Locate ADModify.exe and double click on it.
Click Modify Attributes
On the next screen, select the following
Under Domain List, click the dropdown box and select your domain.
Example: DC=domain,DC=com
Under Domain Controller List, click the dropdown box and select a domain controller from the list. It is best to select a domain controller that is the closest to the machine where you are executing ADModify.
For Show Only, make sure that only Users is selected. Deselect everything else.
Click the green button
This will return the domain. Double-click on the domain object. In this Example that is FineartSchool
This will expand the domain and show the Organizational Unit structure
Navigate to the Organizational Unit where the users that you wish to update reside.
You can double click on the Organizational Units to expand them.
In this example, I want to modify users located in the OU OU 1
Once you have the proper Organizational Unit selected, click on Add To List->
If there are users in sub OUs for the OU that you selected, also check Traverse Subcontainers
This will add all users that are located in the selected organizational unit to the list on the right side.
If you wish to update every user that was returned, click Select All.
If you wish to only update specific users, Shift Click or CTRL Click the users that you wish to update.
Click Next>>>
On the next screen, remain on the General tab
In the middle section of the General Tab, check the checkbox for Display Name
Above the Display Name field, you will see blue highlighted text LastName, FirstName.
Click on the blue LastName, FirstName text.
This will populate the Display Name field with %'sn'%, %'givenName'%
Once you are ready, click Go!
The pop up will indicate how many were changed, how many failed and how many were already set to the desired setting.
Click OK
Wait for Active Directory Directory Replication to complete.
You can check to see if the Display Name has been updated by going to the Recipient Configuration\Mailbox node in Exchange Management Console
Double click on a user. On the General tab, at the very top the name should now be in the LastName, FirstName format.