if there are only places where the fabric is worn, then do the following in those places only. if the whole quilt is shredding then do a complete job:
cover with a layer of tulle, as close as possible in color. very carefully, tack around the worst places. if it's terrible all over, then tack all over. you're trying to stabilize what's left. use the smallest stitches you can, but be sure that you go through to the batting. you don't want the tulle hanging on to fabric that's already fragile. do the same to the back, if necessary, as well as the binding. if there are outright holes, carefully make tiny running stitches around those holes into the batting before you lay on the tulle, then continue from there.
you can display the quilt, but don't hang it flat on a wall. the drag from the weight will tear it apart. fold it and lay it on a quilt rack or (preferably) the foot of a bed, making sure that you refold it often. if you are lucky enough to own a glass case, that's best, because it keeps it dust-free. do not vacuum it. do not lay it in the sun. don't ever use it or wash it again.
i know it sounds dirty, but when textiles are restored in museums such as winterthur, which is famous for it's textile collection, this is the method they use.