Hi XXXX!
There should be no reason for the previous repairs to cause a coolant leak.
The easiest way to find the leak is first with a visual inspection. Check the hoses for cuts and tears where they may have rubbed on something. If you can't find a problem them refill the system and watch for a couple of minutes to see if it leaks back out. If not then you will have to do a pressure test. This pressurizes the system and will force the coolant out where the leaking point is. It could be something as simple as a loose clamp or more complicated such as a leaking radiator. The coolant pressure tester can be rented or purchased from some of your local parts stores.
Where I work we use a labor time guide that tells us what to charge a customer. We charge all customers the same amount of time for the same job! I recommend getting a written estimate first. Then you can tell me what they want to do and for how much and I will check to see if they are on the level.
For starters a coolant pressure test at a shop should be roughly equal to 1 hour of their labor time. We charge a half hour + the cost of coolant, supplies and tax. It usually comes to about $50.00 From that test we can usually give a pretty accurate estimate.
The one complication you may have now is where the car is located. If the coolant leak is severe you risk overheating the engine by driving it. However, if it is severe then usually a good visual inspection can locate it.
Auto Service Technician
ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience!