If the stain proves difficult to remove, you can seal in almost any stain with a shellac sealer. To avoid the shiny spots resulting from the higher sheen over the shellac sealer, seal the entire wall with shellac, not just the stain. If you just clean your air-conditioner filter every month as is recommended, you will reduce your annual emissions of carbon dioxide by about 175 pounds each year. You'll also save money on your energy bills by keeping the air flowing smoothly through the filter. Consider installing shaded skylights to help control the heat getting inside and to keep the house more comfortable.
Skylights are great.
Don't get rid of them, just work with them to make them as energy-efficient as possible.