Your best bet is to call an HVAC service and if they can come out tomorrow, do that. The likelihood that a homeowner can do much of anything is pretty low. And I don't mean to sound like a ****, but the likelihood that you can fix the HVAC but couldn't troubleshoot your breaker is basically zero.
Try to get the power to the HVAC killed (so the humming stops and any further damage, however unlikely, is minimized). Kill it via a service disconnect, by the AC's breaker, or by turning off the T-stat. Open some windows and hope you can get service tomorrow.
If you want to troubeshoot further, start with determining if the air handler fan is working. Does air move in the house (even if it's HOT air)? If not, you may have a fighting chance, because that fan may be within your ability to fix or replace. If that fan is running and the outside unit (condenser) is not working, you're pretty much screwed.
I'd wager you're screwed because the air handler fan (the first one I talked about) would be unlikely to take out the house electrical if it failed, while the AC condenser might be more likely to do so.