If your headlamps are old, then you shouldn't have any problems getting them off! gently warm them with a hot air gun, till they get very hot, the lenses should gently prize off with something wooden or plastic, avoid metal, as this is more likely to chip the glass, before refitting, soak the lens and reflector in hot water and strong bleach solution for several hours, this will leave them looking like brand new when reassembled, use white silicon when you put them back together, for an OE look
Tom