I had no idea I could sculpt either.
My first one just sort of got softer and squishier, but never really went brown. At least, I threw it away before it happened. I guess, because the guts are still intact, and not exposed to the air, that it doesnt rot as quickly.
And because it isnt hollow, theres no way to put a candle in there, so I have no idea what it would look like lit.