It's fairly easy to replace the firing pin spring. Here's an ok tutorial. Just make sure that you are wearing safety glasses the first time you do it and I also recommend that people do it the first time inside a cardboard box turned on it's side so in case you lose hold of it, the parts don't have far to fly. Trying to find a spring on the floor can be a time consuming effort. It'll seem like you need three hands to do it, but holding the slide in your left hand and using your thumb to disengage the firing pin safety is the easiest way I've found.
After making sure it's unloaded and stripping the gun down...
Use a punch or something similar to depress the firing pin, push in on the firing pin safety until the firing pin goes past the firing pin stop, and slide the firing pin stop out of the way. This will be right about the time shit start flying across the room, so be careful.
Clean out the firing pin channel. Since you've got it broken down this far, slide out the ejector and clean and lube that area as well.