Some ways to tell which model/packages:
1. On a 6MT, the sport package will have an SRM button next to the shifter. On a 7AT, not as easy to tell... if it has 19" Rays wheels and a spoiler, probably has sport package.
2. If you have heated leather seats, probably have Touring model.
3. If you have Navigation, you have Touring model.
4. If you have a longer nose with no fangs sticking up from the bottom, you probably have a Nismo model.
While a few people have had overheating issues on the street, most have not. You would probably need to take a fifteen to twenty minute drive and see if the oil goes over 220, but it depends on outside temps as well.
I would be more concerned about the oil issue. While rare, it is serious. If the car has gone 3500 miles or more between oil changes, it is probably okay. Otherwise, check the oil every 1000 miles for a little while to see if it is going down fast.
Some people complain the ECU makes a high-pitched whine (fortunately mine doesn't within my hearing range
).
There are some other very minor issues, but warranty will cover all the problems. Also, you can still buy an extended warranty from Nissan if you are really worried.