I bought the car brand new in 2010. Currently have 26k miles on it and I never had it serviced in the nissan factory...EVER!
0 problem
I think it's a solid car that can run up to 200k miles(At least for the manual transmission) if you take good care of it.
Give it some frequent oil change and you're golden. Just remember.....the more aftermarket parts you add on the car, the less reliable it gets.
And my honest opinion is that you should get the car new. You never know the history behind a used car......especially sports car. People tend to put their sports car to its limit and abused the poor thing. Keep in mind that majority of the 370z owners are in their 20s with over the limit testosterone........and you know how we like to drive these things
Buy it new. It's worth the extra cash. Good luck