There's no cost to list your D5100 it in the I Want to Sell forum or on Kijiji or Craigslist (among other sites). Do it and see if you get a response. If the gear is sitting around gathering dust, that means it's not being used, so what's the point of holding on to any of it?
Sell it all, then use some of the money to buy a Nikonian's membership. Or not.