To sum it up, for the front all you need to do is remove one bolt on the bottom backside of the caliper with an allen wrench, and that will allow you to pull the caliper open and expose the pads. Swap the pads, and retract the piston with a c-clamp. When you open the caliper and remove the pads, the piston comes out as if the brakes are fully engaged. You need to use a C-clamp to retract the piston back into its' orriginal position (check the end of this How-To
to get an idea of what the C-clam is used for.
Now for some reason when I was changing the back ones, I wasn't able to open the caliper and simply swap the pads like on the front, but had to take off the whole caliper and install them that way. But, it is possible to open them just like the front ones (picture on page 23 of protege5.ugly.net) .. I just think mine were rusted stuck or something. If you manage to get yours to slide open, then it's just as easy as the front .. but you have to use an allen wrench to retract the piston (no c-clamp for the rear -- page 25 of protege5.ugly.net).
Check the manual at http://protege5.ugly.net/04-11.PDF
on pages 19 and 23 & 25 to get a better idea of what I'm talking about. It should help a lot.