First you need a spring, maybe the lbs can order one. A bmx shop might have one since these pedals are common to bmx. To service the pedal put it on a vice and grip on the splined shaft. Now twist the pedal off the shaft. Take a pair of pliers and remove the metal ring that drops into the plastic. Now take a standard phillips screw driver and if you have a flashlight you can see a screw on the far end. Unscrew it and after removing the screw tap out the metal band on the other end. Now the pedal will come off the plastic. If you have a spring you should be able to get it back on without too much difficulty although like a lot of springs sometimes things can get difficult. There is also a possiblility you will ask yourself "why didnt I just buy another set of pedals?"