How to get my networked drives to also work on Mountain Lion?
If the VPN is working and the same as on the Windows side, you should be able to enter the server details in the Go > Connect to Server (⌘K) dialog in Finder. If it's a standard Windows file share, just enter in smb://server.local.blah and it should connect.

However if that doesn't work, you'll need to provide more details on how your VPN and servers are set up.