Nissan web site has a diagram of the relay box and description of each relay's purpose. Take a look-
Anyway-- what you need are the 3 relays that go in the two white and one brown position. I don't remember what those others are for, since I didn't need them. The U-Haul kit is those three.
I just do basic towing. I only had taillight power- and was about ready to just patch in to my wiring when I decided to look in the forums and (almost) found my answer. It was pretty confusing at first because the forum I was on was going on about the '04 and earlier and a recall and bunch of stuff under the dash. Anyway- we don't need that in later models, but you do need the relays for the empty positions shown in your (very nice) photo..
I bought the relay set from U-Haul- now I have brake lights, turn signals, and 12V aux. power to my combo-plug..
