I dont think there are any instructions specific to a router chnage, but really they are just ths same as the original install steps from the WIKI less the install certificate, python etc.
As I summary it would be;
Set your Plexconnect to have a STatic IP address in the range form your Router (Best way to do this is by a DHCP reservation on trhe router)
Depending if you changed your Settings.cfg file to contain IP addresses, update this to contain the new IP address
Change the DNS IP address in the ATV to be that of the one given to the PlexConnect machine.
But if this is not working you will need to post all the Troubleshooting information found in the "Read Before Posting" pinned thread so we have enough information to assist you in debuging.