Here's a PDF map (14.4MB!). Enter near Corn Creek Station off 95. Look for the Mormon Well Road on the map. You'll exit the trail on 93. By the time you drive the loop from/to Vegas, you're looking at close to 100 miles. Six to eight hours depending on how many trucks you're with and how many stops you make.
http://www.fws.gov/desertcomplex/pdf/map.pdf
General info about the DNWR here:
http://www.fws.gov/desertcomplex/desertrange/index.htm