Welcome to the forum Big kev,
You're smart to be cautious, but Phantoms are super easy to fly.
Firstly, spend some time learning the settings in the DJI Go App. Connect to your Phantom and do an IMU calibration, gimbal calibration, and the RC sticks. Set your RTH height (it's in Meters) I use at least 60 M. Also check the battery settings (low battery warning, RTH or land).
Take your time learning to fly in a big open area free from distractions, trees, buildings and ferrous metal like fences or reinforced concrete. Pre-flight check: gimbal lock removed, fully charged batteries, SD card, propellers tightened on correct motors.
Start the RC, then the Phantom, then the Go App. in that order.
Calibrate your compass away from anything metal including your tablet, keys, car, ect.
Face the rear of the bird with the camera facing away from you.
Confirm your compass calibrated, and click on camera view. The Phantom will be warming up and getting satellite GPS. When it says ready to fly, push both control sticks completely towards the bottom center position. Release them when the motors start.
Take a deep breath and give the throttle a decisive push up. Get the bird up about 15' high and watch for a steady hover. If it looks good, fly it nearby so you can get used to the controls, and the bird's orientation. Remember, if you let go of the sticks, the bird will stop and hover.
When you land, pick a stable, level surface and slowly reduce the throttle. Slow down the descent as the bird nears the landing area. When the bird touches the ground, pull the throttle all the way down to stop the motors.
Two common questions:
1) Will the motors stop midair if I pull the throttle all the way down? Answer: no, the Phantom must be stable and stopped for three seconds before the motors will stop.
2) Will the motors stop midair if I push both sticks clear to the bottom center position used to start the motors? Answer: yes, this is called CSC and will cause the motors to stop midair. Two sticks in bottom outside corners will also cause the motors to stop. It's only to be used in an emergency.
Go out and enjoy your new P3P!