I don't know if it's possible to learn by yourself (cause normally people need 4 years in university). However, if you're determined enough, you can do that. To give another resource for the background of making apps, you can take a look here...
Start with Nikon I would say, even though the function button is a bit harder to get around, but the color is more true, easy to adjust the angle to make it better.
I don't think you need higher SSD for the update to High Sierra, but the computer might be running slow, but not snail slow as I far as I'm experiencing.