From a D3, the largest print I've made is 24"x36" for a client. It looked great. You should have no problem, it seems you can print quality digital files much larger than many would expect.
I've made prints even larger than that, I've made a 60" print on the long side from single image from the 12mp Nikon D2X, and I made a 14 FOOT square image from the D100. Granted, the D100 image didn't look the best from 5 feet away, it's looked really good from 30 feet away, which was it's intended viewing distance.