I cant fix my nokia 3200!!! Need help urgent!!?

I cant turn it on!! the battery still works because when i put the charger in you can see the battery display on the side going up and down but it is very dark. I think there is something wrong with the button you push on top the turn it on. I took the top bit off and there was a loose thing that has a little black button on it. It is very small. I dont think anything else is wrong with it. Any help or suggestions would be helpful.
Thank you!