I've used the 18-105mm kit lens on my D90 and D7100 for a while and it's a very good lens to carry around. It will render your 18-55mm useless. I got rid of mine and traded up to the 18-200mm for the extra range. The nice thing about the 18-105 is that you can go around without doing any lens change. With the 18-55mm you had, you could have gotten a 55-200 to go with it but that would mean carrying another lens.
You made a fine choice to step upgrade. Personally, I would try to sell the 18-55mm but they are cheap lens and lots of used one out there. Not sure if you would get much.
BTW.. Nothing wrong with buying well cared for used lens, I rarely buy brand new Lens.