The wash arm retainer nut broke in half and the wash arm bearing ring was completely worn away.

I simply unscrewed the remainder of the wash arm retainer nut, removed the wash arm bearing ring and spray arm bearing ring and replaced them; No tools were required. At the same time I decided to replaced the upper wash arm with a kit from Part Select. This did require the use of a philips head screwdriver. The job was real easy and accomplished within 1 hour.