Dear, changing images and icon of app, is not a big task if you are providing images, but your third task changing way of display of content is not clear to me because time in this totally depends on the how much changes are there, and this app is al-ready coded by someone else, so it will also take time to understand the app code and find the place to change, but i can do any type of changes please give me your app name so go through that and after full requirement of the app only i can say exact how much time it will take.