To remove the mag catch you only need to remove the magazine. Make sure the gun is unloaded, then press the left side of the mag catch in until it is almost flush, while turning the catch lock (it looks like a screw, but isn't) on the right side counter-clockwise. When it turns, you have the right place. Then turn it as far as it will go, and push on the left side (the checkered part) and the mag catch will just pop out.
Install the new one in reverse order. If the new catch comes with its own catch lock and spring, fine, it not, you will have to install the old ones before installing the catch itself. Look at the way things go together and you should be able to install the catch lock and the spring with no problem.
Jim
