stella wrote

"I would like to use a TD-8817 to isolate my Netgear wireless router from the internet."
Do you mean that you want to use TD-8817 to hide the Netgear router from Internet?

If so, TD-8817 can work as a router to hide the Netgear wireless router. And to configure TD-8817 to work as a router, you need to contact with Sky Broadband to get some information about username, password, VPI, VCI and connection type.

Once you get this information, you can dial up to Internet on the modem. These FAQs should help you.
For PPPOA: http://www.tp-link.com/en/article/?id=338
For PPPOE: http://www.tp-link.com/en/article/?id=204