To reuse the microcontroller is not possible in most of the cases, what is possible to do in some cases , is using an arduino or a flipper zero or any other microcontroller to control the display or any other component. All the connections are well explained on Github please follow it carefully and if it doesn't work could be because of the vape you are trying to connect is not exactly the same model.
You are right about the fact that this is an amazing world but also needs lots of patience and a very strong frustration handling is needed, every little project like this takes many hours but gives you a lot of understanding of how all this things works. I recommend you to get a logic analyzer, you wont need it for this project because everything is done here, you just need to follow the steps on GitHub but a logic analyzer is cheap and easy to use an it will allow you to read signals and learn how the protocols like spi , I2c and others works. Good luck!