Trish, I just finished doing this in my daughters house. It was quite an involved process and I only replaced the treads and not the risers. You can buy shaped oak treads (and perhaps other woods, but oak seems best for this application)at specialty lumber yards. I saved about half the cost by buying rough lumber and having it planed at the mill. Then I cut it to rough length and width and milled one edge on a router table. The millwork place would do that too, but at higher cost and much longer lead time. I prefinished all the treads with stain and 3 coats of Parks Pro Finisher Oil Modified Polyurethane so the stairs would not be out of commission for an extended time. While this was going on, the rest of the stairs had holes filled with Bondo or Minwax Wood Filler (2 part), and then painted. When all was ready, I removed one tread, starting at the bottom, used the removed tread to measure for exact length, cut using a hand circular saw with the tread up-side down and a saw guide, inserted the tread,drilled holes for nailing, nailed and set the nails, and later filled the holes. This alone took 2 days to work up to the top. It was not a difficult project but you really have to think ahead on how you do things. It also took a fair amount of equipment but did save quite a bit of money and looks great.