Remove the four face bolts and pull the motor out straight. The motor is a 5C face mount into the spindle with a lovejoy spider coupler to the spindle. You will have to hold upwards cradling the motor in your arms to keep it from binding due to the weight on the back as it comes out.
Try to get the assembly to rotate say 10 degrees by using a strap or chain wrench on the motor. If rusted at all clean the small entrance chamfer entrance with a bearing scraper or tiny watch screwdriver
Clean the extension out the front with sandpaper or Scotch-Brite. Fill those top holes and let it sit for a day.
