Checked the grinder/pump well at the bottom of the dishwasher and fished out some aluminum foil, wire twist ties, broken plastic forks, etc. That was fun but it didn't solve the problem.
Purchased new pump & motor assembly and installed it as per Youtube video. It requires pulling out the dishwasher, disconnecting electric, hotwater, and drain lines, and then removing a bunch of clips and connectors. That was time consuming but basically easy ... except that seating the new assembly gasket into the bottom of the dishwasher is difficult. It takes a lot of force to get it into place, and then it tends to pop out of position when you tilt the dishwasher onto its side to install the underside clips. The secret there is that you can wipe a single drop of dishwashing liquid around the gasket before you install it. This lubricates the seal and makes it much easier to seat the gasket. After that everything was basically easy.