Car Overheating/White Smoke out of vents/heater not working

I have a 2002 Chevy Malibu that is overheating, the heater is not working, and when it is over heating white smoke is coming out of the vents. I was wondering what could be wrong, how much would it cost. I need this car to last me at least 6 months and I really can't afford a huge bill and I need my car to get to work. I already fixed the water pump which stopped the overheating for a while, but the problem is back again. Please help