Sorry for the way late response, but I would imagine it is possible. I know it is possible on the earlier G35s. It just required that you temporarily disconnect the speed signal between the ecu and the nav unit. This allows you to program the unit while in motion, but the drawback is that the nav won't update your position on the map until you recponnect the signal. The ones I've heard of that have done this used a switch to disconnect and reconnect the signal.
To bypass the disclaimer screen, there are a couple of products out there, but it will likely require that you access and solder straight to a circuit board. I've seen some products that do this, but at the moment, the only one I can find is here:
http://www.kptechnologies.com/
they use a flash site so you'll have to click on products, then the NavigationOK Bypass links. There are three versions you can choose from. I'm not sure how the aux output on these work, but it sounds like you may be able to use it to allow programming the nav during movement according to that site.