i have taken my headlamps apart on both my old fiesta and saxo. With the headlights i had to hear with a hair dryer (wimped out of using the oven) and heat the glue up and you can peal the glass away from the headlight. Not sure if it's possible with the rear lights though.
I did the same with my mk5 fiesta, was easy, not sure if the lights are sealed with that black gunk though!
pretty cool i reckon...... next mod for me maybe? 
