Since you're beyond warranty, you might want to head over to a local Nissan specialist (sorry, I don't know of any in your area!) and see what they think.
According to the 2003 FSM page BR-142, front rotor minimum thickness is 22.0mm, rear rotor minimum thickness is 8.0mm. You don't need calipers or anything to check, a ruler should be fine (this isn't rocket science

).