I can't comment on the noise, but removing the speedo from a 240D is not a big deal. The easy method is to remove the under-dash plastic piece and push it out from the back. The only part that can be a pain is unscrewing the cable. If you have an 85 mph speedo in your 82 you can also replace it with a 100 mph speedo from an 83. It may be cheaper to buy a used speedo than to repair yours.