BMW Repair: serpintine belt?, worst case scenario, serpentine belt

Question
I noticed the lack of power steering only to follow with over heating as well as batt light on. with nowhere safe to stop, i cranked the heat and hauled my rig to trusted mechanic.  whats the best/ worst case scenario

Answer
Best case?  Serpentine belt broke.  

Likely case?  Broke for a reason.  Like waterpump failure.

Worst case?  Lack of coolant overheated the engine and warped the head, blowing a headgasket.

Good luck! hope it's the waterpump.  Replace the belts and the thermostat at the same time if it is.