I have been searching for an 2002-03 Xterra either NA or SC but wanted to know if there is any common issues that I should be looking at before buying. Is there TSB that should've been done by now or other issues that require part changeout?

Have the transmissions been trouble-free behind the supercharged V6?

There are no real issues to worry about with the 1st Gen Xterras. Personally I would stay away from a supercharged model as I have heard of some issues with them.