Upload & Sell: Off
If sending to Nikon, all you need to do is go to their service website and fill-out and print the form. You'll be paying for the repairs, so proof of purchase isn't needed.
I recall APS has a similar form on their website, though I've never used them.
Nikon USA will repair EVERYTHING that they feel isn't at 100%, the only say you have is yes or no to the total repair. (IE, if they find a chunk of rubber grip coming off, they will replace it and you will pay even though you may only want the AF issue fixed.)