A 'coder' is just a person that can write code, correctly.

PIC is short for PICMicrochip, it's sorta like an enclosed PC, just has no operating instructions on it, so ya have to write up code for it to tell it what to do.

The I/II pots can be used instead of replacing them, provided you connect them up to the wheels gas/brake pedals. Just get the Wiper (center lead) wired up right and then the other 2 ya can mess up if ya want, it'll just act like the button/pedal is pushed all the time until ya swap them around.