How to use the same scripts/interface for different games ?

Hi guys, I'm kinda lost right now ! Here is my problem :I've been working on some kind of prototype for a 2Dplatformer for the last months. I've been using "demo" artworks all the way. Now, I start working with a 2D artist and I want to bring his work and use what I've been working on, but it seems pretty complicated...

The sprites sizes and resolutions are not the same, the camera settings will change also. So here it my question : Which way would be the best for using the new graphics, animation etc ? Should I copy/paste the scripts folders for instance ? Or completely using the demo project and replace all the graphics and animation ? Any help would be really appreciated !

Extra Question : if you guys work with a custom input manager or any devices that you'd like to use in different games, how do you manage this ? Thanks