The factory front sight on the CW9 is indeed plastic and a pair of pliers are the way to get them off. You'll be surprised at how little effort is required.
Make sure you clean the holes out before you mount the new front sight and also use some type of thread locker on the screw.
On the internet, the number of posts do not correlate to actual knowledge.
The notch is supposed to be there as well as the bulge at the front of the frame!
You can't stop insane people from doing insane things by passing insane laws.