First things first.
Find a hand guard or rail that you like and link it. You may or may not have to remove and replace the barrel nut.
If you do, then you might as well replace the FSB. You can get a low profile gas block for fairly cheap ~$50.
If you don't want to buy a new gas block, the cheapest option is to cut down the FSB. You remove the upper portion, (the sight) and leaving the gas block portion intact. Check online for cutting down ar front sight base and you will easily find a bunch of how-to.
I usually try and find a handguard or rail that uses the factory nut and cut down the gas block just because i'm lazy and a pinned gas block is very nice to have, and sometimes a pain to remove (you know who you are BCM).
Troy alpha rails, Samson Evo rails, Rainer Arms rails, Midwest Industries SS gen 2 handguards will all slide over your low profile gas block and attach themselves to a factory barrel nut making install fast and fussy free.