Yeh - dont do it. Its bloody difficult!!
Easiest bet is to use a heatgun - like a paint stripper, and a flat blade screwdriver. But the glue they are held toegther with is like tar, and it is really manky stuff.... it is not something i'd like to do again in a hurry.
personally i woulndnt use a screwdriver, patientence and a strong grip is all thats needed
its takes a bit longer than you think to open them up , use a medium heat and dont leave the heat gun on a single part for to long or it will distort the lens or plastic
Patience... that might be the best bit of advise yet.... i was impatient, and tried to use a screwdriver to pry them open. Paul, what do you do with the black goo... scrape it out or leave it where it is?