Overheating problem?fan belt snapped...helppp.

Hello, i have a ford fiesta 93 LX ,and i was driving yesterday to pick
my girlfriend from the airport. .. i was going quite fast about 90 mph
for an old car like this ..Suddenly the battery indicator flashed  .. i

was in the middle of nowhere so i thought that if i continue driving,
the only thing that it might happen is that the car will die because it

will be out of battery ..and i have better changes to fix it if  i can
get to a garage or in the next exit .instead of stopping in the highway

.
After going for about 4 miles i realized that heating stopped coming
from the car and when i was accelerating i could hear a noise from the
engine like something is happening inside .. i continued for about 12
miles and then the noise became extreme and then smoke start coming out

from the car and then i stopped...
I was waited for the AA guy for about an hour and he said that he cant
repair it  ..and  he thinks that the fan belt snapped and also that the

battery cannot be charged or something.
Before he comes  i tried to start the car just to see if i could and
the oil and battery indicator were on and there was a weird sound but
the car wouldn't start .. i have the car outside a garage and i am
going there tomorrow to ask them ..how much will be to repair it and
what is the problem ..
what do u people think that it might have happened?
any ideas how much will it cost to be fixed approximately?
is it possible that i caused permanent engine failure???

I learned to stop when the first warning appears..i just  hope that the

car will work again..

Thanks Ivan