They're easy to rebuild. Get the seals, number 1 in this picture:

Take your caliper(s) off...
Your pistons will probably have to be blown out with compressed air, put your air nozzle where #7 goes, and protect your eyes from
brake fluid that might spew out...
Clean everything up like new.
I jamb a piece of one-by in front of the pistons to keep them from shooting out like missles... actually, in this picture there's
two one-bys... push out the pistons a little, take out a one-by... push them out a little more... the idea is to avoid "coming out
explosively

"...

You will probably be successful, though I tossed this caliper (and got another fine one to rebuild from Pinwall for $30) when I finally got
it's pistons out:

-Mike