Part of starting the project is obtaining a good understanding of the use of Layers and Outliner. Both are key to the project and will help you manage and control the components and groups of components for the project as they are created.
If you are good at 3d sketching, start making drawings of how you think the project might procede. Some what like story boards that are used for putting a movie together to tell the story.
If you have the wall space, put the sketches, photos and other material on the wall using masking tape. Put the plans on the wall also. Look then over, move things around as a plan for the project starts coming together in your mind.
Them start creating a list of components and how you see the components fitting together to form the component assemblies or groups. Then place the components and groups on Layers and the Outliner. You should them have a good start on a plan for the project.
Create the plan of action, them start working the plan. Modify the plan as needed and move forward. Bob