I've taken apart a G4 iBook, G4 Powerbook, G5 iSight iMac, G4 style Mini, and Alum 24in iMac. The iMacs were by far the hardest to take apart. With the Alum iMacs, you have to take off the glass front, without cracking/breaking/chipping. Once the glass is off, you have to get the screen off. Which involves numerous hard to reach screws. Once the LCD is "free" you have to lift it off far enough to reach under and disconnect the display cable.
Once the screen is off, its pretty much easy going until you have to put everything back together. Then you have to deal with the heavy screen and getting it back into place and screwing in the hard to reach screws. All while keeping dust off the screen and back of the glass.
It doesn't sound that hard reading it/typing it out but the screws that are holding the LCD in are hard to reach and if you drop one underneath the screen you have to take it back out. And the screen, especially the 27in model is heavy. Very awkward to hold it and disconnect the display cable.