A friend of mine is talking about getting a used (certified?) G35 (coupe or sedan depends on color and option available) with 6-sp manual

he said he is high mileage driver (18k - 20k miles a yr), he wonders about the high mileage long term reliability of the car as a whole and also the engine & transmission.

also he was asking options like LSD, sun roof, rear seat head rest. which option package do those comes with?

 

Then your friend may want to look at reliability data published by Consumer Reports. Very informative.