1995 BMW 740IL

While driving my vehicle pulled in the driveway proceeded to turn the key to the off position and it went all the way around. It caught something the second time around, read the owners manual said to make sure the key is in all the way, did this with no avail. Could not get vehicle to turn off. Pulled some fuses to cut off the engine and had to unhook the battery to turn everything else off. What needs to be replaced the ignition lock assembly or the ignition cylinder or both. A BMW parts guy told me I only needed the ignition lock assembly, I attempted to disassemble the outside covering of the steering wheel but at this point it is over my head. What do you think? And how much am I looking at to get this repaired. I need the car desparately to drive but can't do anything at this point. Thank you ahead for any help you might provide.