1996 Pontiac Sunfire Re-starting car after 1 1/2 year hiatu

I have a 1996 Pontiac Sunfire SE that has not been used in nearly 1 1/2 years due to a noisy air-conditioning compressor that needs to be replaced. The car has been sitting in my driveway with about half a tank of gas in it. Before I try to start it up, should I replace this gas which probably has broken down? And if I do where would I dispose of the old gas? What other things should I look out for before trying to start it up?

Thank you.