Is my car axle ok. Or is it my brakes...?

I have a crown Vic. 96. I was told that it was leaking from the differential, and that If all of the fluid went out it would, cause the tires to lock up and stop working. N that it would began to smoke, and dadada. Well I noticed that my brake light was on. and I thought it was tru what the mechanic had said. One day I woke up, and My brakes were completely SHOT! it was nothing. N I rode around n tru enough my back right tire began to smoke, but it NEVER locked up or whatever. But I put in brake fluid, b/c I saw it was low. My brakes light went off, my brakes went back to normal, and Everything was everything. So it hasn't been leaking. b/c the smell isn't strong anymore. And I have to go back to college, which is around 2 hours away...And I'm wondering was it my brake fluid leaking all along. Help me with a little advice please b/c I know nothing about cars...