Do I need to conduct a flight training session? I fly with mouse & keyboard. The trick is to learn the characteristics of the heli you're piloting. For precise movements such as take off and landing, I use keyboard only in 3rd person. For fast flights to get from point A to point B as quickly as possible, I use keyboard for throttle and mouse for control and in 1st person. Anyone who's seen me fly in server can tell you I generally travel at max speed. I used to fly along coast road of Chernarus at around 320km/h at about 15m off the deck.
FWIW, there's a way to keep the mouse from affecting your helicopter so you don't have to worry about it causing issues while learning. Double tap left alt and you'll be in free-look mode. In this mode, the mouse will just move the camera and not your control surfaces. Q=throttle up, z=throttle down, wsad for directional, x and c for rotation while hovering.