Congratulations on your purchase. Those two lenses aren't bad--I have the same pair myself as they came with my D90 when I got it. I found over time that having to carry a bag for the lenses was a pain and I wanted to have just the camera around my neck with one do-it-all lens. Nikon has a very nice and well-regarded lens for this purpose, but I was more enthralled by the Tamron 18-270 because of its wider range. Play around with what you already got for a while, and don't be too surprised if you decide to go the same route I did.
Cheers,
Greg
