What is causing my coolant leak?

I was driving and heard a screaming noise. When I got to where I was going
I parked the car, got out, and could hear a leak. I looked under the car and
saw yellow fluid pouring out. When I was done I drove it home and on a 2
mile drive the car overheated. The next day I bought coolant and put a
gallon into the reservoir so I could drive it to the repair shop. It drove fine
and when I got there I looked under the car again. There was still a leak, but
it was only a drip.
The repair shop said I needed a new water pump, new thermostat, and new
upper and lower hoses. I know thermostat and hoses are relatively minor
repairs, so the water pump is what's running the bill up. Would a bad water
pump cause a screaming noise and a pouring out of coolant? Is there any
explanation for why the leak was pouring out the first time and just a slow
drip the next day?
I've gone to this shop before and was very pleased, but this time they
sounded like a really hard sell. They told me I shouldn't drive it even a few
miles home to think about the repair because it could overheat and cause
major damage. They said repairing the hoses and not the water pump
wouldn't do anything and I'd have to come back again later to fix the water
pump and probably the hoses again. Does this repair sound reasonable?
Screaming noise, pouring coolant, overheat, then mostly holding coolant
and maintaining temperature the next day = bad water pump, bad
thermostat, bad hoses?