Custom Control for ArduPlane

Good Day! I am planning to tweak/customize/override the default controls of the movement of the plane. Like from the taking off to the actual flight instead of doing joystick control I will control using my own idea/custom control. I know it sounds newbie and yes I am, I dont know if this is possible but I believe it is and also the ardupilot is an open source software. I dont know where to start, which module should I override with and where should I insert my own custom controls. Is this possible in any way? Is there some guide which I can insert my custom controls. Coding is not a problem btw cheers! Any information would greatly appreciated