I think some of the walkthrough sites have the fully revealed maps of each area (sure one of them has teh swamp).Basically, running across the middle of the swamp is a band f water. In about the middle, there is a bridge (I think it is depicted in the loading scene for the swamp).
Stay on the path, until you get to the two huts. Behind them is the circular path that leads up to a bunch of Rynjin. Behind them is the entrance.
Tools for Wizardry(r) 7