Help remove wiper arm & nut part number

It is quite easy to remove the wiper arm if you know the trick. Note that the arm is spring-loaded to press the blade against the windshield. This causes the wiper arm to bind against the wiper shaft, making it hard just to pull off.

The trick is to press down on the arm with one hand to relieve the spring pressure, then lift up on the arm where it is attached to the wiper shaft, with your other hand.

Regarding the nut that is damaged, just take it to your dealer's parts dept clerk and ask for a replacement. Don't be surprised if it has to be ordered. While waiting for that hardware to come in, you can go to your local hardware store and see if you can find a temporary replacement metric nut and washer.

If the nut thread was damaged, I hope that the threaded shaft also was not damaged. If it was then you would have to replace the wiper motor assembly which would be pretty costly.

When replacing the wiper arms, note that the windshield has two little dots that show where the tips of the wiper blades should point, when the wipers are off and parked.