Believe the piston size is all the same. Rebuilding them isn't a terribly difficult job, you just need to make sure that everything is clean when you put it back together because any dirt/grit between the piston and cylinder will wear it out fast. There isn't a "how to" I don't think, but long story short, caliper off and drain the fluid, use compressed air to push the piston out, remove the dust seal, then the square cut seal and any others behind (if there is any), then clean and rebuild in opposite order. Be sure to lube everything up in brake fluid when you re-assemble. Also be careful of the square cut seal, they are very easy to tear.