Replacing the backsplash is a job best left to a contractor, unless you are very experienced with DIY projects. It is much easier to install tile than it is to take it out, You will have to chisel out the tile remove the backerboard, install new backerboard and then the new tile or other backsplash material. The trick is to getting this done without damaging your countertop. if you damage your granite, then the project cost soars.