BIGRIG227, my parents have owned horses all my life. We have had goosenecks also all my life. For many years we used a half ton 350 Chevy to tow the trailer so you should be fine. As far as the rear end goes, don't baby this truck if it breaks under normal recommended weight and usage NISSAN will take care of it. As far as hitches and balls go we like the hide-a-ball type since it allows for full use of the truck bed and there isn't a greasy ball waiting to ruin someone clothes. This site shows one type of the hitch I am referring to;
http://www.bageco.com/gooseneck.htm
As far as the weight goes you could lighten your load by looking at aluminum trailers, they are more expensive, but if you are planning on doing any pulling in the mountains you will appreciate the weight difference. Some of the brands we have owned include 4-star, Sundowner, and Hart. Of them all dad says he like the Hart the best. As I said earlier my family used a half-ton to pull our 4-horse gooseneck for years, we made the trip from Jackson Tn. to Eminence, Mo. every year fro about 20 years. If you check out the map you can see there are some good hills on that trip, but very few truck problems were encountered.