Other Fuel System Hoses Lines/piping, And Fittings problems of the 2007 GMC Envoy

My fuel gage suddenly stopped working on my 2007 GMC Envoy. It read that I had 1/4 tank left, so headed to the gas station on a city street. I turned the Envoy off, for about a 15 minute stop, and when I turned it back on, the gage said it was empty. I filled the tank, and it still said it was empty, and the light is on. About 25 miles later, the gage popped up to 1/4 tank , but quickly dropped back down to read as empty again. The light stays on now. All other gauges on the dashboard work properly. The check engine light also came on, and is still on. I made sure my gas cap was on properly, and it was. I just purchased this vehicle on 12-30-15, so I do not know if there were any previous issues . My 2007 Envoy had 61,061 miles on it when this occurred, on 3-4-16.