1994 Chevrolet Lumina Transmission Problem?

When I start my car, it takes around an hour before it will engage into gear. It does not seem to have a problem shifting while going down the road. It has upon occasion died while cruising at highway speed, but will start right back up when I shift it into neutral and try. It dies every time I come to a stop, unless I shift it into neutral and give it gas while I stop, which is quite dangerous. It always starts right back up. I changed the map sensor on it when I first purchased the car about 3 years ago. And the transmission filter was changed when it first started acting up. I have heard several different opinions from friends and I am not sure what to think. Is it a problem that I can easily repair such as a sensor? Or do I need a whole new transmission?