I just finished it.. in two tries.. (am a lvl 20 monk)... first time.. got spotted, and subsequently slaughtered..
second time, was a bit more careful, stayed against the wall, and they NEVER saw me, comming or going.. so i agree that in this case, a lvl 1 could do this mission.. but.. if they get spotted..toast..
One thing that might have made it easier the second time to not get spotted is, i saw someone go in right before me, and they must have gotten the orcs attention... so a good strategy might be to have a buddy pull the orcs to one side, and you go to the other way (i went right after etnering the area)