Modifying a Robot FLR D2-2

I want to reprogram a robot D2-2 which is really cheap (see Banggood for example). The controller supplied is an AT89C2051, and I don’t have the IDE, the programmer and the time to learn, so I decided to remove the AT89C2051 and to try using a PIC.
I have chosen a 16F690 because I have plenty but you can try with another one as long as it has the same pin diagram (for example the 16F1507 is nice).
It is very easy and simple to do! You only need the microcontroller (and a PICKit).”