Remove pump from machine.
Where the black pump meets the metalic motor, you will find several square holes cut into the pump body. One or two of these will allow access to the grub screw.
Check to see if grub screw is tight (allen key, can't remember if metric or imperial).
If not, the grub screw will not be lined up with armature shaft indentation, so remove pump from motor. No need to remove the 4 surface cross head screws. Just the two sunken cross head screws, and loosen/remove the previously mentioned grub screw. Pump should now lift off motor. Move gently as it may be a tight fit or if their has been a leak may be even tighter. Clean shaft, smear a little lubricant on it and reassemble in reverse.
Safe and happy cleaning
Ken