Never EVAR take what the Auto Zone or any other independent shop tells you as the truth. Not that they are specifically lying to you but the scanners all report different information unless tuned for your specific Manu. It looks like their scanner was close but many times it can be pretty far off.
P0263 Cylinder 1 Contribution/Balance Fault
That is the Nissan Specific code. Now I suggest downloading the Service Manual for your year, specifically the ec (electronic or engine controls, can't remember) section and finding DTC 0263 in it and reading about it. It will tell you all levels of diagnostics procedures to follow with and with-out a Consult II programmer.