It won't damage it. Just use a few drops of acetone or nail polish removed to get down in along the metal where it connects to the plastic. It will soften the glue so you can pull out the metal piece. After you've installed the new headband, wipe off the metal end and apply a small drop of general adhesive (not super glue) and put it back together.
Also, the word has been out for a few months that JMoney is no longer selling leather headbands. Some great reviews on these headbands have been circulating around the forum:
http://www.headphonelounge.com