Manufactured Home Metal Roof

Dear Sirs, I sure hope you can help. I have a major problem with a home I purchased a few years back. It's a mfg home that originally had shingles and one of the previous owners had a metal roof installed directly over the singles. Absolutely nothing in between. We are having major mold problems inside the house around the ceilings in the hot humid summer months and the ceilings are so warm it's ridiculous. Of course when you have cool air conditioned air meeting hot humid air you're going to have mold. I have been told to install attic fans, but will this really help? We don't have an attic since this is a mfg home. Is the only solution to remove the metal roof, then the old shingles, then put the metal roof back on? And can the used metal roof be put back on? I really hope you can answer these questions as hot weather will be here before we know it! Thank You!