There wouldn't be much life without the sun. The earth would be cold and inhabitable. It would also be very dark since the sun is responsible for light during the day and the moon borrows its light for the night.
There wouldn't be a "system" of planets. Without the gravity of a star, planets don't orbit at all; they just drift. Any planet in such a situation (and astronomers believe there are many planets that for one reason or another do not orbit a star) would be frozen solid.
Well if the sun had never existed the planets would not exist either, according to the most accepted solar system theory. See, the sun and the inner planets formed from the same dust cloud, the solar nebula. Asteroids and such dwarf planets as Pluto were captured by the gravity of the sun, so if the sun had never formed out of that nebula, the planets would not exist and Pluto would have gone on its path.
Well, I think a lot of things would die from starvation or hypothermia, but some people could survive by growing plants under ultraviolet lights. I mean, it's possible that not everything would die. The world would be really cold and dark, though.