I would suggest, unless you WNT the adventure of setting up SIP and all that, just get a Gizmo account (now that you already have a google account, so that is done).

A Gizmo account is free - and then both you and your wife can video chat over gizmo.

In fact you can setup a new Gizmo account straight from the Nokia itself. And Gizmo to Gizmo calls are free.
If 2 people already have the same platform (Nokia N810 or N800), then a Google chat or a Gizmo chat for Video is the simplest solutions, without having to go the SIP server way.

Quite frankly I dont know why you didn't investigate the first option - setting up a google account to activate the Google chat software on both ends - that is the simplest solutions. Next up is Gizmo.

I also keep Skype installed as a standby in case Gizmo happens to have a bad day (of course I have to give up my video in that case).