Yesterday my furnace blower would not shut off even after I turned the system switch to "off" and turned the temperature down all the way (50). It was so hot in the house I had to turn on a fan and open the windows to sleep. I finally flipped the breaker switches for the furnace and it stopped running but I don't know what to do long-term. Please help!

Your contactor switch is stuck as it went kaput. You need to get a new switch installed. It won't magically fix itself and start working properly either if you were wondering.

What is that? And how much might it cost to replace? And how do I go about replacing it?

Is your unit electric or gas? If electric you have a stuck relay that needs replacing. The relay or contactor is only about $15.00 or so. If it has a light duty relay as most have I would replace it with a higher amperage contactor that is much more reliable. It's a very easy repair. You should get a two-pole contactor with the proper amperage, probably 30-50 amps, and a 24 volt coil. Takes about 20 minutes to fix. DrTom4444

It is electric. I am having someone come out to look at it on Friday so I will mention that possibility, although they will be able to figure it out anyway.