No, Yes (first), No...
No yard dirt in your potting soil... It's too heavy/dense for seeds and you'd probably be bringing in bugs or other stuff you didn't want. Just the potting soil is fine until they are ready to transplant.
Very fine seeds usually want some light for germination (eg impatiens). Other seeds don't need any, but since they are planted under ground, covered, they are in the dark, so it doesn't matter whether there's light or not. I usually start all of mine under lights, because the lights are on anyway for all the things that have sprouted already. They definitely want light as soon as they sprout. A window sill unless you have a great full sun all day window, is usually not enough light to grow seedlings. You probably want to add some artificial light.
No do not use your car as a hothouse. No insulation and too much heat. You will either freeze your little plants to death if it gets cold or bake them if it gets hot. When little, they are sensitive and want an even heat.