Driving home from work Friday morning a heard a "pop" and looked in my mirror to see a huge cloud of steam behind me. I pulled over and discovered coolant poring from the block directly onto to exhaust. After some further inspection I figured out I had blown a freeze plug. It was around 10 degrees that morning, but the plug didn't fail until about 10 minutes into my drive, so I assume the block wasn't frozen and the plug just failed from age/ corrosion. My question is when I order the replacement, should I replace them all, or just the one for now. Is there anything special I need to do when refilling the coolant to bleed the system of air?