One knock sensor under the intake manifold.

12mm bolt intake side between the cylinders. Take out the air box and other random vac tubes and piping. Get a swivel socket in 1/4 in. getting the harness off down there will be the hard part, so loosen it first then disconnect it, then when installing the new one connect it first, then install. I dont recommend trying to make it easier by taking off the intake manifold as it is a complete and total PITA, with the EGR tube being against the firewall.

Go easy when reinstalling knock sensors as the crystal inside can be damaged.

From you local Infiniti tech. . . .