Leak was slow but becoming gradually worse. Pulled dishwasher out from under counter then visually inspected sump while it ran. As soon as the water got very hot, I could see the sump leaking where it meets the stainless pan. Searched for the correct sump gasket without success. Turns out that the gasket is built into the sump for this model. The built-in gasket is very narrow (under-engineered IMHO which is probably why it developed a leak). Thanks to Simon's excellent videos at appliancepartspros.com I was able to pull the sump, remove all the critical parts (diverter, circulation pump, drain pump and aqua-sensor) and then "rebuild" the sump system. The most perplexing part was figuring out how to remove/install the water diverter since my internet searches were unsuccessful. You need to locate the locking latch on the perimeter of the circular diverter housing. Make a mark on the housing and the sump so you remember the correct orientation. Now, while you release the locking latch push down on the circular housing while you turn it counter-clockwise (?) and pull the entire diverter assembly from the sump. Installation is just the reverse except you need to make sure that you properly orient the diverter into the sump housing before turning clockwise and hear the locking latch click into place.
Also you have to be very patient as you figure out how to disconnect all of the plugs on the wiring harness as to not damage any of them. Finally, just follow Simon's video on replacing the circulation pump to get everything put back together again and cross-your fingers that everything works upon testing. Only special tool needed is the Torx T-20 screwdriver.