I've got a d40. The lack of an onboard autofocus motor might make life a little harder on you, but personally I focus manually a lot, so its never been an issue for me. YMMV.

And buy new. A camera's shutter does only have a certain number of actuations in it before it stops working, so better to start at 0 rather than 10,000 or whatever a used camera's shutter count would be.