I've got a reasonable grasp on it, but I'm no expert.
Hayman Reese is certainly the one to look for, with 180Kg of ball weight you'll want the "600" (or 275Kg) kit.
They changed the kit since I bought mine a few years ago but essentially it's the same thing. I think I like the look of the new kit and will probably even fork for one in the not-too-distant future, mine's seen better days!
Make sure you have the appropriate tow hitch. Nissan DID "make" (read "branded a cheaper Hayman Reese") hitch that could PULL 3,000kg but couldn't handle the weight distribution hitch and it would rip the hitch straight out of the chassis. They've changed now, I hear - the new "Nissan" hitch is the same as the better Hayman Reese hitch with multiple mounts in both horizontal and vertical planes.
I also recommend the Tekonsha series of brake controllers. I have the Voyager in mine at the moment, I should have gotten the bloody Prodigy P3 and when I get a spare few minutes I'll cough for one. It's self-levelling (unlike the Voyager) and handles up to 4 axles. I STRONGLY recommend 8mm wire for this one, anything smaller won't carry the amps well enough.