2006 Hyundai Sonata • 4 cylinder Automatic • 56 miles

I have a 2006 Hyundai sonata with 56K miles on it. On Monday (1/31/11) my car would not start and my check engine light was on. I had it towed to the dealership, apparently it was the last day of my warranty. They ended up replacing my crank shaft sensor and my throttle. I also had them do an oil change and top off my fluids.
This evening when I left work I drove for about 15 min before stopping to pick up some dinner. When I got back into my car to head home, my first light I was stopped at I noticed that my car was steaming. My initial thought was that it was the cold outside with the heat of the engine but then I looked at my gauge and saw that my heat gauge was almost in the red. So I turned on my heat full blast, but it was just cold air, it seemed to help bring the gauge down a little. But when I came to a stop I still saw some smoke. Got home and parked, when I got out of the car it smelled like burning.
I have a couple questions, first and for most what could be the potential problem. Second, could this have been caused by something the mechanic did, since this was never a problem prior to me bringing my car in their. Also, wouldn't they have noticed this issue and fixed it during my warranty. It's awfully coincidental that a week after I pick my car up some thing else breaks.

February 12, 2011.

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