One tip and a couple clarifications about the adventure...
(mild adventure spoiler warning!)
North is to the right on the dungeon map (1 -> 1a is going north, the Tooth basins open the door towards #13). People miss that and it will be made clearer in the next printing. Another thing that wasn't too clear is that in the pit in the High Priest Temple, a falling body doesn't count towards the 10 points of damage for the trigger there.
Although the painting in the cabin is supposed to show where one of the secret doors is, I find that people don't remember it by the time they get to the room depicted in the painting. Perhaps prompting them that it's the same room, but with no opening in the wall there, would be an appropriate "gimme" once they reach the room to help make sure they reach the Greater Tombs... but make sure you only give away the location of the door requiring the ritual!
My experience with actual play is that the yellow mold trap is by far the deadliest bit in the module. I've only had one PC death happen after The Big Event of the module and that was because the other PCs thought he was possessed so left him to die.
There were three ways out explicitly built into the module. When I first used this during my normal campaign (before ever thinking of publishing it), they found one of those ways. For the first official playtest, another group of players came up with a way out that I never anticipated.
It's not an auto-TPK adventure.