Removing an O-ring is a common enough task, which for the uninitiated is a bit tricky. It's okay to use the knife blade because it's junk anyway; just don't turn the sharp edge of the knife toward the lands (the grooves that the o-ring sits in.)
Excerpted from a longer movie that shows the entire process of rebuilding a typical faucet. The longer version is the type of movie maintenance personnel might use. The two short excerpts depict specific tasks, excerpted for emphasis, so they can be used as FrogOJT movies -- rapid skill acquisition thru digital video technology. The longer form movie showing the entire process merits it's own CD-ROM-- because maintenance is a different philosophy, a different pace, from production work. There's a higher percentage of problem solving. in the mix.