Starting with the top two steps, place the flat edge of the ripping chisel between the stair tread and stair riser. Tap the rounded end of the ripping chisel with a hammer to wedge under stair tread. Push down on the ripping chisel to pry up the stair tread. Remove the first two treads in order to start taking off the stair riser. Most stair risers are built so that they sit behind the stair treads on each step; number each stair tread by placing the number on the bottom of the tread.
Tap the back of the stair riser with a hammer to remove it. If you have a problem getting the risers or steps off, place a wedge between the riser and the stringer and hit it with a hammer to dislodge it.
Place each riser on the replacement material and trace it with a pencil. Number each riser on the back face of the material so that there will be no confusion when reinstalling.
Cut each riser out with a circular saw fitted with a finish blade; finish blades will have teeth that are spaced close together to make smooth clean edges. Paint or stain the risers and let them dry prior to installing them.
Working up the stairs, lay the risers down and hammer them into place using finish nails. If you are using a hammer and brad nails, you may need to pre-drill the holes for each nail and then use a nail sink to tap the nail under the faced of the riser. Once one riser is done, place some glue down on stringer and set the tread in place. Finally, nail it with a finish nailer.