There are myriad possibilities. I'd start with the battery. A battery can still run a radio or fan, but not be able to crank the starter. I think the cars only came with automatic that year, so the neutral safety switch on the tranny could have gone south. This switch only lets the car start in park and neutral. Sometimes you can get another start or two out of the starter by rapping it a few times with a hammer. If that works, it's time for a new starter.
Auto Zentral Ltd.