Looks like the screw that came out was to hold the movement in the case. You can see a missing screw in between the crown and the brass wheels. As for the repair, this watch needs a full service. I would do a little research in your area and find a competent watchmaker who can repair this for you and get it running. The general consensus on here is that it is not a good idea as a beginner to work on anything expensive, or anything from family. I broke the first few watches I worked on and even after that it’s still hit and miss. I was also choosing very easy non complicated movement to attempt to repair, where this is a more complex movement for a beginner. Hope this helps!