Car problems, what's going on?

Here’s the story. I have a barely-holding-on-to-life ‘99 Elantra; my moronic step-father tried to install a new aftermarket stereo which basically resulted in a torn apart console and a now dysfunctional heater. Air still blows from the vents BUT it is no longer hot and since we’re going through a minor ice age here in the States at the moment this whole predicament is kind of lame.

AND I still don’t have the stereo installed. ::face-palm::

So any ideas as to what could be going wrong here? Fuse, screwed up thermostat, etc.? Just thought I’d throw it out there…