I want to drain the coolant on my IROC but have no idea where to drain it. Do I have to take off the hose that goes to the water pump (since it's the lowest) or is there a plug or petcock somewhere? I'm lost!

 

there should be a plug on the passenger side of the radiator all the way at the bottom. You can remove the knock sensor on the block to drain most of it from the block unless you are going to powerflush the cooling system.

 

Zepher is correct on the drain location however, when I want to flush out the cooling system on my car I just stick a garden hose in the rad with the drain opened up, and let the car run with a constant feed of fresh water from the hose. The water coming out of the return line to the rad will eventually run clear, then you should be good to go.

 

There's a petcock near the lower rad hose as it goes into the radiator.

BUT...

I assume if you're draining/flushing, you'll be replacing the coolant, etc. If you're doing all that, it's usually good to replace the thermostat and both radiator hoses while you're in there. In this case, get a utility knife and cut a gash in the lower hose and drain it that way. This will keep you from possibly breaking your petcock on the radiator (especially if yours has plastic end tubes) and having coolant spray off tubes and going everywhere. This also gives you a little easier drain on the block, too, IMO.

Ed