In my True 1-4076921, GDM12, TR05256605, the one bulb inside at the top has stopped burning. I can't figure out how to change it. I'm afraid I will break something by not knowing the proper technique. What bulb do I replace it with, and where do I get it, and how exactly do I get the old one out and new one in. It is a great cooler and that bulb has lasted for years. Thanks for your response.