I found this info on another site, but it works awsome!!

"First I double checked the pistol was unloaded and empty, and I field striped the pistol by removing the magazine, slide, and recoil spring. Disassembly was very easy; I unscrewed the grip screw, and pried off the grips (they seemed to be wedged in to the frame, a little encouragement with a flat screwdriver helped). I pushed out the drift pin at the bottom of the hammer spring guide rod out (I actually used a toothpick) and had a Tupperware container to catch both the spring and guide rod when the pin was removed. The wolf walther ppk hammer spring was longer than the p-64 hammer spring so I used a pair of wire cutters to cut the wolf walther ppk hammer spring to 1 1/2 rotation longer than the p-64 spring (I always cut longer, its hard to add later). Replacing the mainspring guide rod with the new spring on it was easier than I had thought, I was able to hold the guide rod in place with one hand and insert the drift pin with the other. I replaced the grips and after checking yet again that the pistol was clear, dry fired the pistol. The improvement to the double action was amazing; it went from a 25-30lb trigger pull, to something very manageable. I have yet to put a poundage number to it, but it’s about 1 to 1 1/2 pounds heavier than my friend’s Bulgarian makarov."

He used 17lb I went with the 14lb and the improvement is amazing.

Below is the link to the page to order the wolf replacement PPK/PPKS 9mm(.380) springs.  I ordered item 25914 (3 pack) or for one spring order 25814

http://www.gunsprings.com/SemiAuto/WaltherNF.html#PPKS9mm