1997 Dodge Intrepid won't start

I am a single mom on a very tight budget, and was given a 1997 Dodge Intrepid. The guy who gave it to me said he drove it to work one day and when he got off work, it wouldn't start and that it had previously overheated. He "says" someone "told" him that the water pump 'froze up' and that it would cost him $800.00 to fix it...
I personally don't have that kind of money, but thought maybe, it wasn't something SO costly. My son 'tinkers' with cars, so he is going to attempt to fix it for me so I can have a car again... I REALLY need this car, and it's the day before Christmas. This would be a wonderful Christmas present for me in these difficult times.... Can anyone give me suggestions to get this car running at an inexpensive cost... Such as, the first steps to take to find out why it won't start and why someone told him it's a 'frozen' water pump and will cost $800.00... Thanks a million!