I think I clamped the arm in a vice, then grabbed the hook on the spring with a pair of pliers and unhooked it from the peg. Once that's loose and the tension is off the spring, it can slip out of the notch on the center anchor. IIRC, they're only wound up about 1/4 turn. Replacement is basically the opposite. You need to remember which way they go on (or take a "before" photo like I did.)
[on edit] One thing I forgot to mention earlier: I used evaporust on them prior to zinc plating.
