One of the primary reasons I upgraded from my Murano to the Pathfinder was the added towing capacity. I tow my race car, I tow other cars, I even once helped a friend drag a huge water tank off his property.
The Pathfinder not only comes from the factory with a sturdy integrated reciever hitch, it's got all the wiring for an electric brake contrller already IN the body harness, how cool is that. First off you'll need 3 parts from your local Nissan dealer:
is a 7-pin "RV style" trailer connector which replaces the old 4-pin connector.
is a wiring harness which plugs in under the dash and goes to your brake controller (I'm actually not terribly happy with where I put this, I may move it to that pocket above the 4WD and VDC switches in the center console).
is a 6-pin relay which goes under the hood and provides power to the brake controller wiring harness. It's that brown one there in the picture, plugs right into an empty socket.
Next you'll need an electric brake controller. There are many available, but I recommend the high tech Tekonsha Prodigy, a top-shelf inertia based proportional controller which you can find online for around $100 or at your local UHaul for about $200. If you're uncomfortable doing the wiring, most UHaul locations have a hitch and wiring specialist to do this kind of stuff and their rates are pretty reasonable.
That takes care of all the electricals, but there is one glaring area that the Pathfinder is deficient, the rear springs. They are SOOOO soft, seriously, they must have designed the thing to ride nice and soft at the right ride height with ZERO cargo. Put 400-500 lbs on the trailer hitch and she'll sag virtually down to the bump stops.
There are probably more exotic auto-leveling super air-spring setups out there, but I decided to save my pennies (a lot of them) and use the relatively simple auxillary air support bag setup available from 4x4parts.com. Very cheap, works well, and easy to install, can't beat that with a stick.
The air bags go inside the OEM spring, so you squeeze all the air out and thread them in between the coils.
The small air tube comes out the top of the air bag, through the open upper bump-stop, and then I threaded it through the rear subframe to avoid coming near the hot exhaust.
View of the driver's side of the setup, note you can see the air line coming from the passenger's side, plus always use some zip ties to keep things from wiggling around too much.
Then I routed the air lines up around the spare tire and down behind the rear bumper cover and T'ed them together.
And finally the air line goes to a schroder valve (same type of valve as on your tires), which I installed into the trailer plug bracket.
When you need to tow, use any normal air source to fill the airbags with up to 35psi and it keeps the rear end nice and firm.