Configure Draytek Vigor 2960 with domain controller

I have a Draytek Vigor 2960 that I am hooking up for a friend. They currently have active directory o a Microsoft 2008 server. They currently have an older Adtran router. I have been unable to swap them over to the Draytek and everything stay working with the server plugged into the network. I am fairly good with the routing side but active directory is way out of my skill set. I just need someone that understands how all of the components work together. I won't give remote access but will give you access through some sort of screen sharing application like teamviewer. FYI, I do side jobs for local businesses when I am not at my regular job. I have several of these coming up to be installed soon. Understanding of VLAN's as well as the Draytek switches is a plus. Thanks for looking.