wd-40 isn't as good as penitrating oil you can find at any local parts store. I would try to get the boot off some how and heat it up with a blow torch. Typically if you can get one loose you can pull the caliper back then slide it out. I am not sure of the set up. But if it is that bad you might want to either replace the pins all together or clean them up with a wire wheel. Dont forget to use brake greese whenever putting them back together. Place the greese between any metal to metal contact pionts that are not acutally the pad and rotor.