If you cannot pinpoint where the leak is coming from, you can take it to a repair shop and ask them to do a simple radiator pressure test, you should be able to watch. I have one of these testers, it always comes in handy. Changing the water pump requires removal of the timing belt, so its just like doing a complete timing belt job.

I don't know of an easy way to tell if your water pump has gone bad, but i don't think coolant would be gushing out. Also, the water pump is on the timing belt side- look under the car- where is the coolant coming from? Tranny side or timing belt side?