What a beautiful quilt. I am sure there is a proper way to clean and mend it. You could check with the Folklore Museum at Utah State University, www.usu.edu or 435-797-1000. Another place to ask would be a historical society. Most states have them. A professor of home economics, at the state university where you live might have some answers for you too. Most degrees dealing with fabric have some kind of class about preservation and restoration of old fabric items. If all else fails, any big museum (like the Smithsonian) should have a person on staff who cares for the museum's fabric articles. They should be able to help.
Again, that quilt is beautiful and I agree you should have it appraised and authenticated before making any changes. Then you will need to decide if it is more valuable to you fixed or as is. Sad is the quilt that stays in the closet. Gwyn