I am kind of new in the RC Airplane world. I amb looking into purchasing an APM kit. However, I am kind of lost because as I understand, ardupilot is an extension board for arduino board. However, when I see APM 2.0 seems to be all integrated in one piece of hardware. Do I need to purchase arudino board and APM 2.0 as an extension board or all I need is the last one to have an actual AUV system?