Help with my gas grill and setting up tank?

This will be my first 4th of July as a single mom. I was to start up the grill. The propane tank hasn't been hooked up in about 3 years. I did check and there is gas in there. I cleaned up the grill yesterday. I'm so afraid to start it, is there anything else I should do before igniting the grill. I know I need to turn the gas on before igniting. Do you think the gas is still good since it's been 3 years?? Please any advice. Thanks