Oh boy... I was running this in 5e using the Goodman Games version- by the time my players got to the temple, and got down to the first level.. after they'd done most of the first level they basically said "screw this" and left. We started a different adventure with those characters.
The best advice I can give is you know all those inter-cult faction politics that happen further down? Introduce them way sooner than the module suggests.