Forgive me if im in the wrong section. I would like to replace my FSB on my bushy m4a3 with a new gas block and the centurion HK style buis as i can replace front and rear sights since i have a removable carry handle and the troy mrf-di rail. Is this a DIY viable option? How easy or hard is it? Any recommendations on gas blocks? Thanks guys, and if im in the wrong section i would really appreciate if someone could give me the heads up on where to post my question.