Yeah, that was me.
That is some awesome luck you have then! I found one used one but the dealer would not budge, so I never pursued it. How many miles did the truck have when you picked it up?
I have never heard of that particular leveling kit, but I know a lot of the Xterra enthusiasts go with the PRG kits.
I have yet to add anything to my Xterra, other than new tires and recovery gear. I swapped out the stock BF Goodrich Rugged Trails with 500 miles on them for the Goodyear Duratracs, which have more than proven their worth in the snow, mud, and on trails. Since you have some new Dueler A/T's, you are set on tires for the time being. I would still pick up a shackle receiver, I picked up one from a local 4WD Parts shop for about $30. Using your hitch ball, can be done, but it also runs the risk of the strap coming loose and possibly causing damage. Which leads me to one safety point about straps, don't use a strap that has hooks on the ends. I am not sure what you are using already, but no metal hooks! They can become a deadly projectile if they come loose under tension.
I hope you enjoy your Xterra! I love mine, it has already proved itself to be far more capable than I imagined. Yeah, it's not a straight rock crawler as others have already voice their opinions about, but it does hold its own and is more capable than most stock SUV's/Trucks. I have yet to use my rear diff locker, and have already towed my fair share of SUV's/Trucks out and up trails. Plus, Nissan's 4.0 liter V6 is a fucking beast of an engine, very easy to get the back wheels loose when you want to slide around.