The air bags in the back are stuck in the fully extended position.

Umm. If I am correct in what I am reading, that for some reason your emergency air bags were triggered and deployed because the sensors believed you were in an accident. All air bags are 1 time use. They need to be replaced once deployed. They are not made to be fixed because the vehicles that they usually trigger on are so messed up they are usually totalled and then sent to the junk yard for people like me to rummage through and take parts. Take the car into a DEALER and they will need to replace them.