The initial problem was just a simple blockage on the filter screen...until I dropped a screw. So, I had to take the rest of the insides apart to retrieve it. The original impeller would not come off easily, so I tried to pry it off. Naturally, that caused the threaded portion to break.
The new impeller went on much more easily than the old one came off, and the dishwasher is back in action. Simple repair; there's really not much to the inside of this thing.