There is a product that I use when servicing gas fireplaces that works pretty good. Google search "Rutland White Off". In a lot of cases it takes just about everything off and the glass looks brand new. If it went to long without being cleaned, it could be permanently baked into the glass. As far as removing the glass, every manufacturer uses there own style of clip. Check around the bottom of the fireplace where the controls are for a latch or possibly screws that are holding it in place, sorry, without looking at it, it's pretty hard to answer that part of your question