Dave,
You would be better off trying to sell the camera kit and taking the money and buying a D200. With the announcement of the D3100 you are going to have a harder time but that is a nice lens, I have it, so you may give that a shot. Adorama will also buy used equipment if you want to try that. To try and swap an entry level DSLR with a semi-pro camera will probably not get much attention. No offense.