I've overhauled motorbike calipers, which I think are smaller and more complex to work on than simple 2 or 1 piston car calipers. I've generally not had any problems, remembering to follow simple basics.
Such as taking notes of shim positions before/while removing the calipers, and during pad and piston removal.
I usually pump the pistons out to the point they nearly are free (using the pedal, or in my case break lever !) then ease them finally out. Bike calipers are usually multi piston (4 or 6 per caliper), so a block of wood helps to squeze all the pistons out to.
Once you've got the pistons out, its a simple matter of carefully cleaning out the corrosion around the seals, and re-assembling.
Its a labour intensive job, but on a motorbike makes a massive difference - the manufactures are pants at providing good weather proof calipers. On a car, thankfully manufacturers do a much better job, and put reliabillity above brake performance and weight.
Enjoy !
