The coolant system pressure test will not harm your coolant components anymore than running the engine since the pressure at which the radiator cap releases excess pressure is the same pressure you will apply to the cooling system.

As for identifying where the leak is, you will have to be more specific. I would suggest taking a picture where the leak is located on your vehicle and including in the picture some way to definitively identifying the location such as pointing to it with one of your fingers or putting a piece of tape on the hose where the leak is.