HELP! Turning an EA Door into an Archway

Love the doors included in the Realm of Magic set, but would love some to be arches too. Does anyone know how I would go about turning some doors into arches? I've seen it done before but cant find any for this set. 

I have taken a stab at the tuning, removing the door locking/doorbell ringing operations, but I dont know how to edit the mesh to remove the doors. 

Thanks!