Well it is pointless to stain AND paint it. The stairs must be stripped down to bare wood to be stain. The stain and seal them according to the instructions. If paint them you will just need to clean and prime them. Then paint on a few coats.
Painting is not a simple work as you think it is. In order to have a good finish to the work that you have done you need to rub the material well and then start painting in an up down fashion.
