All are very pretty, you sure got a great bargain. Good for you.
Yes, I would back them with plain muslin and bind with a color to go with them, or close. To wash them I would spray with shout or something like it and soak for about 5 minutes and agitate just a few minutes, the soaking will soften anything that may be on them and loosen the stains, this is how I wash all my quilts. Good luck and enjoy them.