2004 Chevy Cavalier WATER PUMP

Hit a rock, put a hole in oil pan, within 5 sec, engine shut off, car sit for three months before any work was done, replaced the oil pan took out all the plugs, filled with oil slowly got engine to turn over, put plugs back in and it fired up, runs great no knoks no pings, but now for some reason I get no water circulation, have replaced the thermastat twice, took it to a garage, I was told they had no idea why it wasnt circulating, do you think that its simply a bad water pump or possably the gears that turn the water pump, im lost with this I just want to know that their is hope even if it is some kind of gears that dive the pump, im willing to pay the 800 to 1000 dollers to change the water pump, but could I be looking at much more?