Creating a 3D character on ready-made models

There's a 3D character model. Replace the head of the character with the head of the photograph (including the hair). You don’t have to do a high detail of the face, as long as it looks like it. In other words, the person who looks at the result must understand that it is his face.
The price was not indicated because you want to understand the complexity of the task and the time to complete it.