My friend has an old house with an old gas furnace. After she had her thermostat replaced she continued to hear her furnace running after it kicked on. She has no money, and like me, is a woman of a certain age. She's afraid to call a repairman because she's afraid that he'll tell her to get a new furnace. Is it possible that my friend and I could fix this with instructions? We are NOT skilled. She is more hopeless than I am. Her husband has dementia and is always cold. Thank you.