Do it first, but no "washing", just soaking without agitation in the washer. Spin that out, fill with water to soak again without agitation, and spin the rinse water out. Repeat the same way for a second "rinse", and dry. Never in a dryer. It's best to dry flat if possible---outside in the shade ontop of a clean sheet, with another clean sheet ontop if it's under a tree and birds may soil it. If that's not possible, then hang over a clean clothesline, preferably shaded. Then proceed with your repairs. Good luck. It's great you were there to save it. I saved one once which looked like it had huge areas stained with old motor oil. It was from the 1880's. The black stains didn't come completely out, but they're faint now.