Welcome to the forum, glad to have another enthusiast on board. You'll find your way in TG3, but I advice you to look over as many older threads as possible and use the search button. There's a wealth of information, and samples out here. And start working in the node network, and name your shaders appropriately.
As for the light; you can decrease the sun's strength, and use light sources at specific locations (inside rooms). Experiment with values for strength and distance, etc.