What to do with the bird eggs?

The small tree in the front yard has a nest in it. One day I went to look at it and a Mommy bird is sitting in it. I know she's sitting on eggs because she sits on it 24/7 unless she is to get water or food. Before I knew she was there I leaned against the tree and she flew away. I checked on her nest again and she was back. Everytime someone glances at her or even opens the front door, she flies away. She always returns but i'm scared one of these days she will leave and abandon them. I would like to care for them myself if she does. She is a small house sparrow so I know it is okay if I do so without a permit. But my questions are.... how would I care for them? Is it possible to build an incubator? Please I need to know, the tiny chicks inside want to be out one of these days! Like I said, I want to care for them. I've been wanting to hatch an egg for a long time. HELPP!!!