5D3 focus screens - for sale by Haoda?

Once the 2 screws come out, the metal plate lifts off. Under that, the metal wire(s) you mentioned is actually one single one that goes around the sides and top. Very simple to remove, just pushing down on the top part (which is the part that's hold everything in against the frame) and the metal wire holding frame falls forward along with everything behind it.
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Nick Dollimount
Canon 5D Mark III
Hobbyist - https://www.facebook.com/nickdollimountphotography