Well since it is all Linux it should be similar. You will probably have to adjust the config files to match the Knoppix names. Have you checked out IPCop? It is a distro designed to be a broadband NAT/Gateway/Router and is very easy to install. In fact they also have a way of backing up the config files so that if your HD failed again, a simple restore of the config files would bring it back to life.
I hope this helps.
James