Well this is my fist post here....new member.
You can prize the cover off to reveal the two screws holding the unit in place, (start prizing from the front) look on Youtube there are some videos showing cluster removal but what i would suggest is fold some fine wet n dry sandpaper a couple of time and slot this between the contacts behind the switch to clean the contacts, this will help reduce the situation before purchasing a complete unit which is possible to have a similar situation if purchased second hand.
Any way good luck