tutorial of intalling chdk is here:
FAQ - CHDK WikiAny chdk build is safe to use and makes NO damage to your camera.
chdk is loaded from SD card, if you encounter any problem(but you will not, nobody reported any damage caused by chdk) just format your card and chdk is gone.
even canon service can not detect the usage of chdk without having your sd card
(my camera was repaired under warranty after using chdk for months, the main panel had some mechanical problem)
by the moment there is 2 feature rich build: "Allbest" and the new "Collaborative" build, which is based on Allbest build just it has some extra features, a little bit experimental yet.
there is a special build created by microfunguy dedicated to stereo photography
