No need to change the arm, just the rubber wiper. You can change rubber wiper at any accesories shop or DIY. I have changed my rear rubber wiper , it is easy , just buy the right type only . 
Sorry to say for those not sure, kindly do not give wrong info for others like need to change the whole arm. TQ .

you can send your car to those bodyshop and get them to check on the rear door hinge. Have you involved any accident before for the rear hatch area?
Rear wipers very easy to remove. just open the cover and unbolt the nut to take out the rear wiper arm. as for the blades, can replace the rubbers only. if your arm looks old or broken, you can get them replaced for less than RM 40.