With the hammer back, move the thumb safety up and jiggle it outwards until it comes out. That will let you pull out the grip safety. Then you can remove the pin that holds the hammer in as well as the pin that holds the sear and disconnector.
To remove the magazine release, depress it most, but not all the way in, and rotate the screw about 1/4 turn counter clockwise. You have to get the magazine release in just the right position, or you won't be able to turn the screw, but once its in the right position it should turn easily, but only about 1/4 turn....then the magazine release will just pop out.
With the magazine release out, you will be able to slide the trigger out the back of the frame.
If you have an ambidextrous thumb safety, you will have to remove the grip panels and pull off the right side thumb safety before doing the first step above.