So does replacing the brushes as effective as getting a new
heater blower? If so, that $40 kit with detailed instructions
should do the trick for me. If not, the best prices I've seen are
$151 for the blower and $275 for the blower with the fan
attached.

I'm just hesitant to spend that much time and money only
to find out the problem is in the regulator.

As far as I can tell, the vents are opening and closing. When
I took a drive on the highway this afternoon to see if I could
feel any air coming out of the vents and check if would come
out both hot and cold, I shut down the center and passenger
side vents so everything would come out on the driver's side.
It did.

The back seat vent opened and closed properly as well.

Banging on the panel where the fan is didn't do anything nor
did trying turning the key on an off while changing the cc
settings.

Bill