Ive taken the heater controls a part before and when you separate then the back of the numbers before you get to the ink has a thick molded white plastic surrounding it. We couldn't think of any way to get it off as its too difficult to sand it down and it doesn't come off :(

Ive took mine out before and got to a bit that looked like it could seperate to give access to the bulbs can't remember too much about it at the moment. The only reason I had it out is because I was painting the housing around it. Like I said im gona buy a cheap second hand one and see if its possible. Atleast that way if I break it ill not be left without a heater lol