Conceptually, the design is simple. There are just three parts: The body, the "iron" (blade), and the wedge to hold the iron in place.
The iron has two parts has two parts: The iron itself and the attached chipbreaker, an 18th century innovation that is widespread in modern bench planes, both wood and metal, but is still somewhat controversial.
There is a chip out of the "tote" (handle), but that is essentially cosmetic. A more serious problem for actually using it is that the mouth is too wide:
This is very common on older wooden planes. Since Mia's aunt wants the plane to be used, not just sitting on a shelf, I will need to repair that. There are well-documented procedures for doing this.
Once that is done, and a few other simpler tasks, e.g. derusting and sharpening the iron, the plane should be quite usable. I checked the sole with a couple straightedges and it appears to be perfectly flat. There are a lot of woodworkers even today who prefer wooden planes, and some companies still make them.