There's also a new map with most of these trails, Trails Illustrated Linville Gorge / Mount Mitchell, that you should definitely buy if doing this ride w/o a local guide.
This ride is serious business. I did it last night after work ending in the dark, so it's fresh in the mind. You need decent backcountry and riding skills. If you make a wrong turn, you can end up 2 miles and 2,000 feet in elevation off course before you realize it. If you do not know how to read a map with confidence plus have good fitness and skills, do not try to do this. And, as is, plan on 6 hours- it may take more, may take less, but 6 hours is a good plan. 4 hours is a good time for fast locals not racing.
Personally, I don't recommend this for an out-of-towner ride w/o a guide.
On another thread, you asked about fish hatchery riding- it doesn't suck, that was tongue-in-cheek, I'm guessing, but at this time of the year, there's a lot of people/summer camps plus a key linkage trail (Cat Gap) is closed from spring-fall to bikes. Caney Bottom and Daniel Ridge, however, are great rides that are open (with far too much tourist/summer camp traffic) this time of year.