There shouldn't be any problem buying it out of state and bringing it back home. Most any dealer should be willing to do this. Many Prius owners did this to alleviate their wait. You will have to do the registration and title paperwork yourself though.

You are correct on the service issue. Disclaimer from Nissan's web site:

Altima Hybrid will be available in California, New York, Massachusetts, Connecticut, Vermont, Rhode Island, Maine and New Jersey. Service of hybrid components outside those states is limited and could involve some days' delay.

I wouldn't let that sway you too much though. The hybrid system itself doesn't require much maintenance. And repairs shouldn't be common. Toyota's hybrid system has proven itself quite reliable.