If you're going with a non-extended handguard, you don't need a low profile gas block. If you're going extended you will.
To remove the RRA handguard you'll remove the gas block (keep the tube installed if you're going to reuse it, but separate the tube if you're going to a different block) first. Then loosen the jam nut (take it back towards the receiver) by applying some heat (good heat gun or torch) to it (to get the locking compound tacky, not burning it out) and using a chisel tooth spanner (we use an adjustable model from Grainger, but the YHM wrench is also pretty close) to move it. Then take the handguard tube off of the barrel nut external threads (2.5"+ nylon strap wrench works best for this). Then th4e barrel nut itself using a barrel nut wrench or wrench head. Then install th enew handguard using the instructions from its manufacturer.
Steve/RRA