I've just had to do mine. I was barely able to move the arm by hand. It's been fine for 4 years I've owned the car and then just started playing up in the last 24 hours.
I found that removing the wiper arm and circlip, then, with the tailgate glass horizontal, spraying some WD 40 round the spindle and leaving it over night made removal very easy.
In fact, removal, cleaning, greasing up and re-assembly took less than 20 minutes this morning. I also gave the motor spindle a quick squirt of white lithium grease. My rear wiper has never worked so well, or been so quiet.