Modifying DOOM images,characters, and levels?

For a High School English project I need to make a video game about Dante going through Inferno (yes, I know there is already one). I thought that I could modify the game DOOM and make my own levels, and images for guns and such.

This is a very old game, and modifying it should not be too difficult. Does anyone have experience with this, and what tools should I go about using to do this? I am proficient in Java, Python, and C#... If that helps at all.