I boiled some water. Then I stuck a pencil eraser in the head. After that I dipped mostly just the helmet in the water. Finally, I attached the head to the torso and kept on twisting the helmet until it got loose and fell off.
I hope this works for someone else!
The hairpiece you link appears to be the same mould as the standard non-movie Wonder Woman figure. The hair falls quite close to the back of the minifigure torso, so there's no room for a neck bracket.
If you're looking to add wings to your Wonder Woman, it might be worth investing in a helmet or hairpiece that doesn't cover the back of the torso.
The Lego Group has a policy of not producing modern looking weapon accessories.
If what you are looking for are 20th century style weapon accessories for mini figures you will need to look to non-Lego third party vendors.