This video shows a Syma 3 channel helicopter being torn apart for no reason other than to show the sequence in which it comes apart. I have many of the small copters by Syma, and they usually do not have to be worked on.
But if your copter needs a tweak or a repair, it may look like a hopeless pile of parts if you get ahead of yourself. NOTE, that all parts are bagged and tagged upon removal, with their srews. Most copters have as many as five DIFFERENT SCREWS holding them together. Be sure they get back in the locations they came from on the 3 channel helicopter, as you put it back together.