Pop the pulsator cap off, used a large Phillips screwdriver to remove it, bang on it a couple of times to break loose and gunk holding it in place, then lift it out. Easy fix.
But be careful not to drop the bolt into the tub [on OEM part]. Because if you do, it will roll into the sump area forcing you to spend a couple of extra hours taking the whole darn thing apart. Seriously, hold onto that bolt tightly.