I'm not a mechanic either... But I know enough to do 100% of the work on my car rather than a shop. There's numerous things... Radiator blockage, water pump failure, *thermostat* (yes dnkygirl, you could be right!
), blocked hose (highly unlikely, but could happen). The head-g may be leaking and could be a reason why you are 2 quarts low, but that would not be the reason why you're overheating.
I hope I helped, but I think I just added to your list of unbearables. Sorry, but I just wanted to aid another neon enthusiast from the dread of overheating.
Matt