shooting coolant out of reservoir/defunct heater

[sd88supra]

I took off the thermostat housing, and there was no thermostat! Not only that, but the heater core was bypassed! My mechanic supposedly bypassed the heater core because the hose that goes into it was leaking and he couldn't find a replacement so it was a quick fix. At that it was done poorly, I'm more than sure air is getting in through there. So I go on to put in the thermostat, and the bottom bolt broke! So now I have to either drill it out or hammer a flathead screwdriver in to take it out (if any of you have done this before, please let me know how to go about it. I also bought a bolt extractor in case the hammering doesn't work).

I didn't have time to work on it until today, but I was delayed even more because the douchebags at Auto Zone and Kragen don't know how to find that hose without matching it, and I don't have the hose to match it. Does anyone know the diameter size and proper name for it? There's a good picture of it in the BHG repair sticky. The hose goes into the firewall on the driver's side.