I would try
http://www.retroclean.com . Have seen lots of good comments about it for vintage quilts. However, if the stains were created by wood acid, cleaning won't help. Many vintage quilts were permanently damaged by storage inside a cedar chest. Wood contains acid, and fabric in direct contact with wood will gradually be eaten away. It starts by looking like a stain but eventually becomes a hole. If the stains are along fold lines, that is a clue that it might be acid damage.
Although you can spot treat a top, it's risky to wash a top before it is quilted. Aside from seams ravelling, the fabrics in the top can shrink at different rates, causing a lot of distortion. It is safer to quilt and bind the top, then wash, as the quilting stabilizes the top and takes control of shrinkage. (Once quilted, fabrics cannot shrink more than the batting allows.)