If I want to replace the glass (crystal), without replacing the case, how do I remove the glass? Do I just need to press hard enough to pop it out, or is there some special trick? I don't want to damage the old glass or the case, but it seems the glass is glued on there. The model is a Gulfman, by the way. I have already removed the metal ring, and disassembled everything else, so I am left now with just the glass and the case and it seems the glass is glued on.