2005 Mercury Mariner Ignition Switch Replacement Cost

If the ignition switch and ignition lock cylinder are one component, replacing the switch will be very difficult if lock cylinder fails. If the lock cylinder works properly, the ignition switch is generally not too hard to remove. In most cases, the steering column plastic covers will be removed, and the lock cylinder will be turned and released. The ignition switch can then be taken out, after removing any obstructing or retaining hardware. Once the ignition switch is removed, a final bench test may be conducted to make sure it's the problem. The new switch will be installed and the lock cylinder will be put back in place. 

Replacing the ignition switch does not normally require replacement of the ignition switch lock cylinder, so the same key is normally used. If the lock cylinder is replaced, the ignition key will change as well.

The ignition switch is typically not a DIY job. Newer ignition switches have more advanced security systems and are more difficult to access or remove. With most modern vehicles, it's best to take it to a technician.