Ok, my headliner is sagging in the back. I do not want to replace the whole thing because the rest of the liner is fine, except for some staining. Can I just fix the sagging in the back with some adhesive? If so, how do I fix it and what adhesive should I use? In addition is there a way to dye the headliner or clean it, while it is still up there? Mine is very stained it looks like the previous owner threw their drink up there!