bulbs are fitted nfrom behind the unit, take out the fog light and twist the cap, bulb is inside but if its rusty that is prob the projector, you can take the lense off but i wouldnt as it will never seal again and probably break when u remove/refit it
mk 3 foglight are notorious for leaking water in, sounds like yours have done at some point
what i did with my anniversary smoked ones when i got them was seal the hell out of them before they even saw my car, they have never leaked in, but my old standard ones never did either and i didnt ever seal those...
