I just ordered a new servo from x-heli will be getting it soon. My question is to replace the servo (its the one that controls the left side of the cylic on a HBK 3.) what else is involved in setting up the servo so it does the same movement as the old broken one used to?

I don't really know how all the mixing is transfured from the Txtransmitter to the Rx reciver because all servos move at the same time to change the pitch of the blades. only one or two move when you control the cyclic. Where is the brain in the heli or the controls.
Im new to RC( have flown friends small co-axelheli got pretty good after a few charges on the battery) and arejust trying to get a better understanding of how everything works together.

Any comments are welcome, Thanks