To take off the cap I used the tip of a flat head screwdriver to firstly start it off then worked my way around. It does take some force but the clips attaching it are strong so shouldnt break.
Once you've started to release the cap from where its sitting you'll need to give it a bit of force to completely remove it from the clips inside. Then when you have finally removed it you'll need a philips screwdriver to take out the couple of screws that are holding the indicator to the cap.
Small flat head screwdriver, philips screwdriver and a bit of bravery as you tug it from where its positioned. Good luck ;-)