The click-wheel assembly is glued to the top of the casing and cannot be removed until the circuit board underneath and the LCD screen are taken out. Follow [guide|423|this Guide] to figure out how to take it apart. Once the logic board assembly is removed, apply a downward force to the menu button and then to the rest of the buttons once the top part of the click-wheel is loosed and it should pop right out of the casing.
To put it back in just get a flat object that can fit inside the casing and apply pressure to the bottom of the click-wheel to get it to stay in. Check the inside to make sure everything looks flush before inserting the logic board assembly to ensure that a ribbon cable will not tear when trying to reassemble the device.