I disassembled the pump and got the impeller turning with a pair of channel wrench pliers. However, it doesn't seem to be turning too freely. I would think it should spin like a bicycle wheel but it doesn't. I think a bearing replacement is in order. Is that a DIY or should I find a re-builder?

BTW, don't use a socket wrench to tighten the drain plugs, use a screwdriver instead. It's easy to apply too much torque with a wrench and shear off the plastic plugs. Guess how I know that?