.. How do I navigate the labyrinth?

You can't do it by yourself.

And, each screen, the labyrinth changes randomly.

Have you talked to the cannibals lately?

If you run through all the dialogue options, they'll tell you about the head of a navigator.

That head is the only thing that can get you through the labyrinth.

How can I get the Head of the Navigator?

Once you're in the labyrinth itself (i.e. one screen after the spine-ladder and the faces-in-the-rock), look at the head of the navigator.

Follow its directions.

Be sure to look at the head on each screen.

Following its directions can be tricky, but keep at it and soon you'll arrive at LeChuck's ghost ship.