I did this swap with no diagrams at all, I have the Factory Service Manual for QX4 but you don't need it. I wired power direct from battery, and made relays using factory Nissan relays (doused in silicone to make them waterproof). Each headlamp uses only three wires (1 12v high beam, 1 12v low beam, one ground). I didn't connect the headlight leveling actuators, though, so the headlights don't move as I drive. I wired the city lights into the factory corner lights.
Let me know if you have any questions, as I did this swap already. They are GREAT lights, you're gonna love them!
PS - do you have a 99 or a 99.5 QX4? As the lights and radiator supports are slightly different, for a 99 the lights *should* just bolt right in. For the 99.5, I had to cut out a significant portion of the radiator support. (in the 99.5 update, the qx4 went from glass to plastic headlights)
Mine:
When we were cutting out the radiator support: