Hi John,
Thank you for your reply. I think you hit the nail right on the head. I watched the video several times and applied the instructions to my Actiontec C1000A modem. There are two areas, in my modem, to configure the DNS settings. One is under WAN Settings and the other is under DHCP Settings. The DNS works fine if I set it up under either one or both areas. Once I go to Service Blocks and create a rule to block port 53 and apply it to the device's ip address, the device completely stops working instead of routing to the Norton DNS service. I just receive a message "web page cannot be displayed."
I'm not sure if it's an issue with my modem or my lack of understanding. I don't think Centurylink will be very helpful, but I guess it wouldn't hurt to call them or Actiontec for assistance.
Thank you for your help.