Really, you can find people selling their factory hitch for pretty cheap and it is only $56 or so for the 7 pin harness from Nissan of Turnersville (
http://www.YourNissanParts.com/ ). Even if you bought the hitch and the wiring harness from that website you are still over $100 cheaper than the package from the factory. From what I have found there are three main hitches for our car, Valley, Hidden-Hitch, and Draw-Tight. But the only one that offers a 5,000lbs towing rate is the Valley (factory). So while the other two are a tad cheaper they can only tow 3,500lbs.
Edit** When you check out at Yournissanparts.com type in thenewX.org in the discount code box and you'll get a 10% discount.
Edit v.2** I double checked YNP and was a little confused by the wiring kit they have, but here is the 7 pin harness from courtesyparts.com
http://www.courtesyparts.com/Mercha...n=PROD&Store_Code=CP&Product_Code=999T8-N5005