Before you grab your screwdriver to change that breaker why don't you go ahead and call 911 ahead of time and get them en-route to your place? Tell them to come on in and bring their defibrillator with them so they don't have to go back out to their truck to get it.
We have a "Main Breaker" out by our meter. Every time I do ANY electrical work inside or outside the panel, I shut it off. It kills the power from the utility meter, inside all the way to our breaker panel and beyond.