I'm afraid the "User Hooks" is only implemented in copter. You've probably already seen it but we have some developer information on the dev wiki although honestly, it's a bit out of date. Sorry I can't be of more help. You may also be able to get the attention of more devs by posting to the drones-discuss google groups email list.
Thank you anyway.
It still should not be too hard to insert my own code right? The hurdles I am facing are mainly compiling my own code in the existing files and getting used to the coding styles the developers used. I'm not used to C++ coding style in the Arduino environment.
I don't think it's that hard. The easiest way is to add a new line to the list of scheduled tasks. You should find the list maybe 1/3rd or 1/2 of the way down the ArduPlane.pde. A screenshot of the list is also on this wiki page.