Hey - I just did this!

Rebuilding the calipers is an easy job.  Pop the pistons out one a time - I
used a bicycle floor pump and just wedged the rubber tube into the caliper.
Make sure you put a block of wood between the pistons to protect them.
When the piston comes out it will sound like a gun shot.  Clean up any
corrosion/goop on the pistons and reassemble with the new seals.  I used
brake rebuilding gel from the local FLAPS as it made everything slide
together easily.  I also cleaned everything a couple of times with this
gel.  To get the seal around the top of the pistons I used a high
technology tool made of a large C-clamp and a jam jar lid of the
appropriate diameter.

If the calipers are scored you are in trouble.  I believe they are chrome
plated and cannot be honed.  Probably not cheap to replace.

 >OK, 25-point tossup question here (am I dating myself?)
>
>Awhile back, I picked up a front disk caliper rebuild kit,
>since the rubber in mine is  more or less non-existant. St. John
>makes no mention of the job, and Clymer mentions blowing the
>pistons out with compressed air, and don't screw up or you'll
>never get the thing back together again (slight gloss on my
>part ;->).  The recent thread on rebuilding clutch cylinders
>brought this to mind.  Am I best off scheduling some down time
>and take the calipers to someone, or does someone have a
>reassuring shade-tree procedure for this?
>
>TIA and Cheers!
>--
>Todd R. Schroeder          |    Without vision, a people perish.
>todds@sunnet.chotel.com    |      Proverbs XXIX:18
>'71 Campmobile