At first I couldn't understand why someone would use a separate A/D converter when most of the PICs have them built-in. The answer was in the code: it was written by a Maxim guy to demonstrate the Maxim A/D converter. Definitely the hard way. The code seems to support only one axis.

The PIC16C54C shown in the schematic is an OTP meaning "one time programmable". You have one chance to get it right or it goes to the landfill. They offer UV-erasable windowed parts for code development but you need a UV eraser to use them. The '16C54 is the oldest surviving member of the PIC family. Newer PICs are flash-based and can be reprogrammed many times.

If your heart is set on the '16C54:

Erasable = PIC16C54C/JW
OTP = PIC16C54C-04/P