Installed my AP today buddy, and i was paranoid a little just like you are but once your into it its a very easy installation! Read and follow the instructions carefully from the booklet that comes with the AP and you'll be fine! The only berry i had with it was the near 30 min wait for the AP to save the stock tune when i was hungry and had to go to the toilet and i wasnt allowed to open the doors during install! lol
Havent driven the car yet, not until later tonight anyway so im pretty keen to see how it goes with the Stage 1 OTS tune!
Good luck and have fun