With the older model I would cut a strip down the middle and peel it back. Much of the resin stuff they used internally can be cleaned away with a Dremel using a brush attachment of some sort. The wires were surface mounted to the board so it was pretty easy to replace once you could get to the board. Once the wires were replaced I then Shoe Goo the strip back in place and heat shrink the whole thing with clear 1 cell heat shrink from the old round cell days.