mcgeehe: You want to talk to the troll, and then the guy in the village about saving the troll. Do this before ever playing dice with the guy in the hut. Don't even talk to him. Once you get the troll to agree to fix the bridge you can go into the hut and examine the head. If you play dice with him first I don't think there is a way to get the head. It has to be done after you get the troll to agree to fix the bridge.
After all that play a game of dice with the guy in the hut, once you beat him there will be a way to say you want the she-troll head as a reward.
I'm recalling all this from memory, but i'm 90% confident it's the way to get the she-troll head. Hope it helps.
Edit: Yes you need to beat everyone else in dice poker up to that point or else he won't play you. Sorry I don't rember all their names, it's been a while. IIRC correctly there's 3 guys in the pub, the book store guy and then the guy in the hut.
I did that, I did the poker face after the troll agreed to fix it if I find the head, but when I won against the head dude I couldnt ask about the head, 2 traps and a sword IIRC