This unit advertises being IPv6 capable on the box, but I just confirmed with Netgear Tech Support that it cannot serve as an HE Tunnel Endpoint. With OOB firmware. When I get my Linksys "unbricked" I am going to try other linux based firmware on it and see if it can be a tunnel endpoint.
Don't you have CLI access on it?
You can also use 6to4 - HE.net advertises 192.88.99.1 so there is some chance that you will use HE's tunnel with 6to4.
The only Out of Box access to the WDNR3700 V3 is via the routers webpage, cli is not an option.