Can you please tell me what programs or applications are best to use to overlay a face from a photo on a video? I want to replace the face in the video, but I don't know where to start. What are some free or inexpensive options, and how hard is it for a beginner?

For quick and easy, try mobile apps like Reface or FaceSwap Live - they automatically replace faces in your video, but may have watermarks in the free version. For more advanced processing on a PC, Adobe After Effects with plug-ins like Deep Motion or Face Off will do the trick, but you'll have to deal with masks and tracking. Very difficult indeed. I can also recommend free video face swap https://wishapp.ai/ It is much easier to work with it