pretty simple. It will be self evident when you see the clip/spring.....
Might want to get new wear sensors.. as they are cheap
http://catalog.worldpac.com/mercedesshop/sophio/image.jsp?title=Brake%20Pad%20Sensor&url=http%3A//img.eautopartscatalog.com/live/N103026105PEX.JPG
Some simple tricks....
Just open each bleeder and push the pistons back all the way in using the old pad and a lever between the pad and disc [ screwdriver works]..then close the bleeder and drop in the new pads and wire them up..opening the bleeder makes piston movement back into the caliper much easier and it also gets rid of the crap in the caliper , thereby not allowing it to be pushed back up the line...plus you will not have to watch the res level b/c it will not change/overflow due to piston displacement change required to accomodate the thicker new pads..
You can get the correct parts right here at the top of this page.