We have a lot of employees that get married or divorced and require a name change on the system. We create them a new user account in AD and on Exchange but how do we move everything over to the new account or is there a better way of handling this?

You should never create a new account for them, as that loses the SID associations. Simply right-click the user account in AD and choose "rename".

Obviously renaming is a wise solution. Although you can export the PST file from the old account and import into the new account, you need to grant permission again to every shared resource. It is same if there is any certificate and so on. TechNet