1987 GMC S15: Turned on AC, died, won't start& headlights quit at same time

What is your question?

Filled the gas tank and headed down the road, I got a lil warm so I turned on AC for first time this year. Immediately after flipping the switch, the truck died and oddly, now I don't have headlights either. I put gas into carburetor (?) and it started for maybe three seconds. Dash lights, door chime, brake lights come on, all fuses check good, battery is charged. It sounds like it might start but won't. Things I have done in the past month are new fuel pump, new starter, new fuel pump relay, new alternator, new plugs. I am at a loss. The book is no help to me. I am a single mom and have never been trained on auto mechanics, so I don't know all the terminology. Thanks for any help.