I ordered a new heater element and two new washers. Here's what I learned after watching their video and then doing the repair:
1. I didn't need to order new rubber washers. Even though they weren't in the diagram, the new heater came with new rubber washers along with the nuts.
2. I didn't need to pull the dishwasher out from the wall. I was able to reach underneath and undo the nuts. Your experience may vary depending on how meaty your forearms are, but it is possible.
3. Once I reassembled, it still didn't work! Pull out your instruction manual, and run a diagnostic cycle on it to reset everything. I had to hit 3 buttons in a 1-2-3 sequence 3 times to activate the cycle.