transmission and other problems

I have a 94 3.1 corsica, and it is doing some strange things, can anyone figure this one out? The transmission will not shift on its own any more, it has to be manually shifted, the speedometer and fuel guage dont work any more. I just had to change the alternator, as these things happened at the same time, all of these pronlems started at the same time, altornator too.Small things also, are happening with this car also, the door lockes dont lock when the car goes in gear, the dome light stays on for about 4 min now,not the normal 1 or 2 min, anyone now what could be causeing this?