Sounds mullered to me. As a self professed 'competent home mechanic', I would rebuild them with new pistons and seals. Here is the info you will need:
Full bleed instructional video
Full service instructions
New seals and pistons
I am sure that someone with experience with these will be along shortly to give more advice. You will need to drain the brakes before you strip them, yes. Seems the spring is hard to come by, you may want to email Hayes and see if they can send you one...? But, if you opt to rebuild them yourself, maybe get some fresh pads to have them totally like new?