2004 QX56 Changing spark plugs, how difficult?

It wasn't very hard to do on the Titan. I suspect, you might need some combination of extensions and such (I can't recall exactly) but I don't recall anything special about doing it. The only potential difference might be witht he engine cover. Not sure if the QX version will be in the way or not. Just go out and look. Each ignitor coil will just need a 10 mm socket to remove. Once you remove those, its like any other DOHC spark plug replacement.