The extractor is held in place by spring tension and it shares the same spring as the safety detent. You will need to remove the safety to get the extractor out. Its an odd set up for an extractor that was done away with on the improved 31P version. The extractor also tends to get dirty quick underneath it.
You need to start by taking out the firing pin retaining plate. Once that is out you can remove the pin in back of the slide and to the right of the firing pin. You will then need to remove the right side safety lever by pushing in the pin in the center of it then sliding it off the safety. After that you can remove the safety and that will expose the extractor/safety detent spring.
Be careful, once you remove the safety the spring tension is gone and the extractor can fall out. There is also a pin at the extractor end of the spring that can fall out and also the one for the detent that may be launched when the safety is removed.
I also had a problem with shells occasionally not extracting and took it apart to see what I could do to fix it. I found a lot of dirt under the extractor and cleaned it out. That helped but it still did the same thing on occasion. I ended up cleaning up the claw with a jewelers file and replacing the extractor/detent spring. That took care of the extraction problem but I also had to smooth and polish the safety detent since the stronger spring made the safety movement stiffer. It extracts fine now and I can still easily work the safety. Also, one other thing I did that may have helped is polish the chamber.