HOW TO FIT GEAR CABLE TO RENAULT TRAFFIC VAN?

ONE PART OF MY GEAR CABLE(ENGINE END) IS WORN. IT SEEMS TO BE MADE OF PLASTIC AND IS A PUSH FIT ONTO LEVER AT ENGINE END. THE PLASTIC IS WORN SO KEEPS JUMPING OFF DURING DRIVING THEREFORE I CANT CHANGE GEAR. IS IT POSSIBLETO HAVE A STEP BY STEP INSTRUCTION ON HOW TO REMVE AND FIT NEW CABLE. OH HAVE ORDERED NEW CABLE AND IT SEEMS THEY COME IN PAIRS DO I HAVE TO CHANGE BOTH