I would definitely understand audit sampling. I am betting top dollar that I am going to see a simulation on audit sampling. Murphy's law, right? The only topics you arent completely comfortable with are the ones that show up in the simulations!
I agree with minimorty that you should understand sampling. I also struggled with this after reading both Becker and Wiley. What helped me was to read that section of my old audit text and then do several MCQ to reinforce it. The textbook explanation was a lot clearer to me.