If it's a 740, the ignition lock is essentiall 1 piece with a removeable electrical switch on the left side. About your only option is to remove the electrical portion and try lubing it from the back side. You could also try getting a new key at a DEALER cut from the key code. They can get the code from your vin. If the lock needs to be replaced, the steering column has to come out. If you have a 760, The lock cylinder is easily removed by taking of the plastic covers from the column, put the key in position 2, and press the small brass button above the cylinder and remove the cylinder. Takes about 2 minutes. If it is a 760, get a NEW lock cylinder right away. When they get worn to a certain point, the key won't turn at all, and you can't get it out. Then it gets ugly. Drills, chisels, swearing, etc.