Wow, I have no idea what was in my head when I typed this. Please disregard.The original front sight base on the M-16 is aluminum, which is also a gas block, and they work fine. Unless your SPECIFIC design of gas block has a history of problems, it should be fine.
That said, if this is a weapon you will be trusting your life to, and the steel gas block gives you more peace of mind, then swap it out. If this is a fun gun, just leave it.