While your waiting on an expert response, I researched your question and found someone was also wondering how to winterize their dishwasher. The link provided is for a different model but it will somewhat give you an idea of what steps you need to take in order to do this project. I have provided the link below. I hope this helps!
Greetings! As you are properly planning, winterizing household plumbing fixtures is a good idea when they will be left in a home without heat. The following link is offered to explain the steps for winterizing your dishwasher.... Best Regards!