1996 Buick Regal other

1996 Buick Regal 6 cyl Automatic 170000 miles

My car was over-heating and I had some one change my thermostat then we found a big leak and then we change my water pump as he was chainging my water pump he had a hard time puting on the belt he told me that my tension bolt was old and need to be replace so he put a screw for the mean time untill I can afford the tension bolt other then that they fix that problem, my question is after they put the new water pump their was another leak but no were near the water pump area but more to the back, what and were could the leak be I asked this question cause I dont want to run my car cause it has this big leak dont want to take a risk and I dont want to be buyin parts that I dont need.