Very easy to strip and rebuild the calipers. You need an external/female torx socket to undo the bolts which are cheap and readily available, you can get away without using a brake piston removal tool if you pump the pistons out before you remove the calipers.

All the seals and pistons are available from Honda or as pattern parts, its best practice to replace all the seals before reassembly including the small o rings that seal the two halves (you need to split the halves to remove the pistons) use red rubber grease on the new seals during assembly.

Have a good look at the grooves where the seals sit in the caliper, if your calipers are sticking corrosion in these grooves could be the cause, pushing out the seal so it nips up the piston. If its not to serious you can get away with cleaning the grove with a dremel and rotary nylon brush.

Personally I would rebuild my calipers before buying second hand as used calipers are likely to be in the same condition as yours anyway, spend the money on a rebuild and you know your brakes are good.