How would you completely rebuild a Casio fx-87DE X ClassWiz to run AI locally?

I have a Casio fx-87DE X ClassWiz and want to completely modify it so that it can run AI locally.

My requirements are simple:

* Everything must be contained inside the calculator.
* No Wi-Fi.
* No Bluetooth.
* No connection to another computer while using it.
* From the outside, it should look like a normal Casio fx-87DE X.
* The additional hardware should be hidden inside.
* I’m willing to open it, modify the hardware, replace parts, solder, and work on it using my computer.
* I’m willing to buy whatever parts and tools are necessary.

I’m not looking for a simple software trick. I’m willing to rebuild the calculator internally if that’s what it takes.

If you wanted to build this yourself, how would you approach it from start to finish?

And specifically: What hardware, components, tools, and equipment would I need to buy?