You need to improvise a bit. My ffx had potentiometer problem , i decided to change it , because the inside of potentiometer was completely fuc**d up! I replaced current potentiometer , now my wheel has a HOLE looking at the bottom of my wheel , because in other way potentiometer don`t fits inside. After that i thought : "god damn , what have i done... Oh some glue will help". In this way i`m racing about 6months and no problems since then.. Later i will take a pic of inside my wheel , you will see..
I can guarantee that if you look closer you`ll see some screws inside that "plastic planet". Just look carefully , it is nonsence that you can`t open the most fragile place , in what way then repairers manage to open and repair the wheel if it get`s broken?