My gearshift is locked on my 2007 Lincoln Navigator

Does that not have a cable shift and a modular column ? You can take the column to the bench. The parts are all available individually for repair and rebuild. Just the upper section is present when you have a mod. col. design. Lock cylinder, and mechanisms are accessible with removal of the plastic covers. Operation can include braking first, turning the key,pulling the gearshift, and combinations of turning the key some and trying it when, lets say, the battery was dead and you had to push the vehicle. The actuator for release when braking has a 15A fuse. If that was melted, the fuse can be replaced. Now, what is happening with the mechanism in yours ?