Changing the sole on the Bernina walking foot is pretty easy. There's no need to force it off. Just turn the little screw on the side until the sole is loose enough to remove. Turning the screw doesn't loosen anything, it kinda prys the metal arms apart. There are 2 bumps on one side of the sole and one bump on the other side, and holes on the inside of the arms to match them.
The #5 foot's flange goes through the middle and past the needle. So when you do a blind hem, the flange keeps the thread loose.
The #10 foot only has a flange in the front. It's great for stitching straight lines, but pretty useless when you need to do a curve.