"Fixed Sights" can not to be removed; they consist of a notch or groove machined into the topstrap, along with a front blade of the proper height.
I suspect what you are referring to is a dovetailed, windage-adjustable dovetailed rear sight. Dovetailed sights drift out from left to right, and install from right to left. You'll need a bench block, the proper brass drift, and a light (4 oz) hammer.
Installing a new adjustable rear sight will almost certainly require a new front sight, as the adjustable sight is bound to be taller than the original.
The front blade can be removed if you have the knowledge and the tools (I'm nor sure if a Taurus front blade is staked, sweated, or pinned).