Battery/Gas Gauge

So I had a random issue today. I went to start my car this evening, and it wouldn't start. The lights on the dashboard (warning, maintenance, etc.) lit up, and the headlights and interior lights were extremely dim. Figured it was an issue with the battery. Used my husband's car to run errands and came back about an hour later. We decided to try starting the car again, and it turned on, headlights and interior lights were normal brightness, but the gas gauge is at one bar, which I know isn't possible because I have only put 166 miles on this tank of gas. I reset the gauge at each fill-up so I can track how my mileage changes. The maintenance light is also still flashing. None of these were issues I had last night, so what could be causing all these problems? Can I fix it myself, or do I need to take it into my Toyota dealership?