Frigid Furnace

Hope was cold. It was 1am on the coldest night of the winter.  The furnace blower wouldn't turn on.  Shit.
I futzed with it until 2am and gave up.  It was time to bundle up.
I'm not an expert on furnaces, least of all the electricals that drive the motor, but I figured I should give the repair a shot.  Once again, my lack of trust of repairman was haunting me.  I did some research during daylight hours and many online comments pointed to the capacitor.  It was a $10 part so it wouldn't be a big deal to just try it, but I prefer to definitively diagnose problems before throwing parts at them.  I got out my trusty voltage detector and it seemed to indicate the capacitor was not working correctly.  Only one of its wires was showing a voltage.  I assumed this was the input, so the output wasn't working.  I had my smoking gun.
I will also point out the absurd filter wedged in the furnace in the photo above.  I don't know when that was done, but I feel lucky the house hasn't burned down.  This filter is completely unnecessary, considering it is trying to filter incoming air that just passed through the standard filter, which I have replaced twice now.

After receiving the new capacitor I installed it and wanted to test it.  In order to test with easy access, I needed to keep the access panel safety switch pressed.  You can see my safe setup below.

Shockingly (literally), the furnace fired up and the blower spun to life. SUCCESS.  Then I tried to reinstall the capacitor in the bracket and shocked the crap out of myself.  Almost made it without an injury; maybe next time.

I am curious what would have happened if I had called a furnace repairman.  I suspect I might be paying for a new furnace instead of a $10 capacitor.  I'm almost tempted to put the old one back in and have a few people take a look at it to see how honest/competent they are.  Maybe next time.