Henry has AMAZING customer service. I had a problem with my GB when I first got it, they sent ups to come and pick it up, and fixed it, had it back in two week turn around fixed.
If you do want to get another front sight post (which you can) and taller, as bugeye pointed out, all you have to do is make sure that the dovetail is the same diameter, and it will be good. You might even be able to get a fitted one or two straight from henry.
To knock it out, you just need a mallet and a punch. When I am moving mine I use a metal punch, with a piece of leather between it and the sight to protect the metal. It will slide if you tap on it (fyi, same method to change windage adjustment) just tap all the way out, and then line up and tap new one in.
