Posted By:
Max WederI can recommend Fraser Spafford Ricci,located in the Pacific Northwest, who are conservators for such institutions as the Vancouver Art Gallery and the Seattle Art Museum http://www.fsrconservation.com
While their services are not cheap, they have done some amazing work in the art and paper restoration field. They'll tell you what can be done to remove stains, and whether it fact it can be done.
Max