its not terribly difficult. if you need pictures Kramer did a guide a while back to open a DT770, they're pretty much the same.
pull of the pads, just pinch a sopt and pull, slowly work your way around until the entire pad is loose. new you'll see a foam sheet covering the driver and a plastic ring holding it in place, grab a small flat head jewelers screw driver. there's a notch at the top ot the ring, stick the screw driver in therre and you can pry the plasetic ring off. (Do not put too much pressure, you risk damaging the driver with your hands) eventually it will pop off, when it does you'll see the white circle... thats the driver. if you carefully tip the headphone it should fall out into your hand and you can see where the wire connects.
like I said Kramers thread has pic's.... he's a god when it comes to stuff liek this