Fixing a car door lock is a relatively simple task that can be completed with a few basic tools. The most common problem with car door locks is that they become jammed or frozen, which can prevent the door from opening. In most cases, this can be fixed by applying a lubricant to the lock cylinder and working the key back and forth until the lock loosens up.
If the lock is still jammed, it may be necessary to remove the door panel to access the lock mechanism. This is a more complex repair, but it can be done with a few basic tools and some patience. Once the door panel is removed, you will be able to see the lock mechanism and identify the problem.