Don't want the sheets.
Stains probably could be removed quite easy. Fold the sheets loosely. Place them in an old-fashioned washing kettle, or any other big pot. Ad plenty of water with washing detergent, and then boil the washing for a while. Gently stirring the soapy "broth". Make sure the cloth gets submerged often.
Rinse gently, because it is a really old fabric.
Chances are that all stains are gone by then. If not, drying them outside, placed on a lawn, on a very sunny day, may do the rest.
