OEM Timing Chain Kits?

Courtesy Parts (Nissan) is where I ordered all my parts when my guides went bad. They were very good on price and support the forum. No kits that I know of but they'll have all the parts you need.

CourtesyParts | Genuine OEM Nissan Parts & Accessories

This thread was also very helpful when I went thru this (mainly just for the parts needed):
http://www.thenewx.org/forum/15-how-tos/47728-how-change-timing-chain.html

All i had replaced were the secondary timing chains and their corresponding guide shoes, as well as the o rings called out in that thread. The truck only had a little over 60k miles on it when they went bad so I didn't see the point of replacing everything else.

Most recommend changing the water pump when doing this service. That link to the xterra thread will show you what others have changed as well.