First, Put it back together with hand stitching, don't try to make it right at this stage, just get it back together as best you can. Try to make it lie flat as you pull fabrics and batting together. The stitches you put in at this stage are for reinforcement.
Next, look for fabrics that come close.
First, whipstitch a patch on the back.
Second, Find bits of batting that come close to the original. Is it cotton or polyester? It looks like cotton from here. Put them in with hand stitches, kinda like darning.
Third, Layer in your replacement fabrics, whipstitching them in place.
All this will take time. Just remember that quilts acquire character, sometimes by accident. You will love it all that much more.