^^ All of the above. ^^
Additionally, if the muzzle device IS pinned, you can still get the FSB off, but it may require you to engage a gunsmith's services to have the current device taken off (it'll ruin it, so be prepared for another muzzle device and a pin/weld job) so that the FSB can be removed. If you are just wanting to move to a FF handguard setup or wanting a handguard that would otherwise cover up the gas block area...there are some companies out there that make 2-pc gas blocks that clamp together top/bottom that will allow you to keep a pinned/welded muzzle device in place. Most barrel nuts for use with a FF handguard will slip right over the pinned device so that's a non-issue. Just cut off the current FSB with a dremel or suitable tool for the job and move on from there.
Anything else and you should be GTG with the basic set of tools required for any assembly/disassembly work on an AR.