Corsica: Uncontrollable Shaking

I have a 1988 Corsica with 125,000 miles that has had always had a slight shaking problem while in idle. The problem would only go away when I put the car in either park or neutral. This has been occurring since I purchased the car about 2 years ago. Earlier today, I drove the car to school and nothing was wrong. That night, I went to drive and the shaking was rediculous. From 0-10 the shaking would ce completely out of control and then after that it would settle down slightly. When I would push down on the gas the accelleration was extremely slow. I took the car home immediately and the shaking continued until I put it in park and it calmed down a little, but was still shaking more than it ever had in idle before. I just wanted to know things that could be wrong and possible prices. Thanks!