I believe that you can do that. Put your code in Stage/compositionReady.
if your image is called 'image' and your button is called 'nextButton'.
When you mouse enter on the image it will show the button and you mouse out it will hide the button. Use the same code for the back button.
sym.$("image").bind('mouseenter',function(){
sym.$('nextButton').animate({ 'opacity': 1.0}, 1000);});
});
sym.$("image").bind('mouseleave',function(){
sym.$('nextButton').animate({ 'opacity': 0.0}, 1000);});
});