Just the arm or do you want to remove the mechanism too? The arm is easy, remove the spare tire and lift the cap covering the base of the arm to expose the nut. Use a wrench or socket (13mm I think, maybe 10 mm) to remove the nut and then pull off the arm.
As for the mechanism, I'm not sure how it's sealed to the door but first remove the arm and then pull the lower inside panel off and it should just be a few bolts to remove the mechanism.
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