Easy Diy
Not sure how the book says to install a new one. BUT. I have removed mine using a typical M-16 pick to roll the spring out of the mag catch notch. You need something with a right hand hook to remove it and a left hand hook to put it back in. Either that or the other way around. Is easiest that way, or you could try a very small screwdriver. Once the spring is lifted from the mag catch, the catch simply falls out.