Similar to the 20", I have converted a non-working 17"iMac into an external monitor with a resistive touchscreen. All connection go through the neck and any computer can be connected via VGA or DVI signal to extender cables at the back to the base. Likewise the touch screen hooks up via USB port through the back of the base. I have detailed construction of this mod at:

The iMac G4 forever changed the way I viewed computers. With some modification it can be used as an external monitor or updated all-in-one computer.