Product review (5 stars): A quick repair without being cleaned out
I was getting ready to load the dishwasher the other day, and lo and behold, the lower spray arm didn't move when I bumped it!  I took off the spray arm, and found the lower bushing (properly called a seal,) was badly worn.  I suppose that something had to wear out after 15 years.
Anyway, a quick search found the part number for the seal, and an Amazon search found the part, and it was even available with Prime 2-day shipping, and the price was only 50 more than the base price from the retailer's parts warehouse.
Two days later and my Kenmore dishwasher is up and running great again!