WON'T START!!

My son has an '04 Mustang and a need help. It won't start. It was stolen and wrecked a few months back, but started and ran once. I was told to check the fuel inertia/safety reset switch. Should the red button be all the way to the top or closer to the bottom but not touching the bottom? When I turn it over, I can not hear the fuel pump, but it was changed out less than a year ago. I checked the fuel pump fuse under the hood, and it's good. Where do I go from here? I am not knowledgeable about these things, and don't have the $$ to take it in right now. Any info is greatly appreciated. He's driving me crazy! and for some reason thinks "mom" can figure this out. also, don't know if this applies, but his aftermarket stereo equip. was stole including fuse under hood, and wires were cut and yanked out (thought maybe they may have pulled something loose).