Here is a sample of a quick test I did, though it doesn't completely match the .tgd file any longer (I had the total reflection too high, and the specularity too low, but it still came out great). I lowered the total reflectivity, upped the specularity, but it took almost the entire night to render so I quit.
I know the 'hills' don't match dunes the best, but it was more of a test to see if I could get a true sand look. I'm still working on it.