If it is a newer 870 than it is threaded. In that case then you should be able to unscerw it with not too much effot. More likely it is press fit. If it is press fit then well that is going to suck. If you want to do it yourself, then you'll probably have to cut it flush, drill it out, and then tap it for the new bead. If it is press fit, I would take it to a smith.