Welcome Luke.
Mileage shouldn't be a problem if it's been serviced correctly. Hopefully it's got history with it has it?
Take a look at the service schedule for the 350, that way you'll be able to tell if it's lacking or wanting for anything. Link: http://www.350z-uk.com/topic/31110-service-schedule-for-a-350z/
Can be heavy on fuel depending on how heavy your right foot is.