Is it an FR-5 I need? Also I noticed it said 40NM on it so I'm guessing I need some sort of torque wrench to tighten it up?
FR-5, any Shimano one, basically any cassette lockring tool other than Campy (there's only 2 standards and Campy is much less common). You also need a chain whip. If you want to use a torque wrench then any that have 40nm or 30 ft-lb in their range will be fine, such as most common automotive ones. In that case you'll need a lockring tool with a square drive in back such as the ones made by Lifu or Pedros, or a 1" socket for the Park ones. Personally I only use torque wrenches on aluminum freehub bodies and even then it's a pretty minor concern. 40nm/30ft-lb is pretty tight. The best way I can describe it is as it's reaching full tightness, you'll typically feel one last firm click of the teeth of the lockring and cog engaging, such that it would be hard to imagine any unintended forces overcoming the thread preload and getting the teeth to disengage. That's tight enough.