If there is a local quilt shop in your area, contact them for a reference to a reputable quilt appraiser. If there is not a QS in your area, go to the AQS website and they can provide a referral for you. The appraiser should be able to tell you the best method for cleaning it.
http://www.americanquilter.com/members/appraisers/
Here is a link to their list, but you might be interested in starting at their home page to view some of the other links on the subject. It is very informative.
Hope this helps :D