Rail System Recommendations for Bushmaster 6.8 ???

Let me start by saying the AR is completely new to me. I got a new Bushmaster 6.8 (BCWA3F 16M468) about a month ago and now I'm looking to upgrade to a new rail system. My plans are to add a vertical grip (probably Larue FUG) and light (probably Surefire) in the new future. I'm looking for recommendations and advice. I'd like something that doesn't require me to do a lot of specialty work - I'm handy with tools, but not a professional. I was looking at the Daniel Defense Omega Rail 7, as it appears to be one of the best and easiest to install. What do others think?

What are the requirements if I go to a longer rail? I've read stuff about a low profile gas block, but I'm uncertain as to what that relates to.

Again, the AR is new to me so please forgive the newbie question. I do appreciate any help you can offer.