I am in the process of installing the MK2S upgrade. As instructed, I printed the gcode parts. I could not get the ABS that Prusa shipped with the kit to stick to the bed. I had a spool of ABS (Manufacturer Unknown) and use it to print the parts. During assembly I had real problems with the Extruder part I printed. All of the holes were too small. I had to really work to get the square nuts into the hole slots. The PINDA would not fit in the hole. With reluctance, I drilled out the mounting hole so I could get it in. I could not tell but I hope I did not drill it so much that it was past the wall thickness of the hole. Apparently the ABS I have has greater shrinkage than the Prusa ABS.
I did not have any PET Filament to print the PET gcode files and had no way of knowing what they were. While routing the cable I discovered it was asking for the cable holders. I was able to go the the MK2S parts list and figure out what they were. I have another printer ( a CR-10) and printed the cable holders using PLA. I am now ready to finish the assembly.
I wish Prusa would have included the ABS parts in the kit.