When you go to refill, I'd highly recommend using distilled and/or 'baby water' from the grocery store, as well as adding something such as Redline Water Wetter. They both will do great things for keeping your cooling system happy.
I'd also recommend buy a new petcock to install once you drain the coolant. The plastic petcock (drain plug) gets brittle from all the heat. I recently had coolant leaking from the radiator, jacked up the car and realized it was from the petcock. The head snapped off, leaving just the threads inside the radiator. Took me over an hour to drill the threads out. Just buy a new petcock for $4 (online price, I think dealer charges like $15) and install it instead of the old one. You will thank me later.