Could see water leaking from pump discharge coupler. In retrospect, I should have also purchased the pump rebuild kit. (Would be good to list parts commonly replaced together). Computer was broken and did search/ordering on an iPod touch).
There is a special wrench used to install the coupling sleeve. The spray arm base is kept from rotating by two plastic tabs in the tub. Snap these off and you can unscrew it from coupling sleeve without any special tools. I put a screwdriver through the base to get enough torque to shear off the tabs. Put some RTV sealant on the spray arm base before screwing it into the new coupler. This will hold it in place and prevent leaks at the joint.