The computer is flashing that some things need to be serviced

First off. This is my first SUV (I have had older SUV'S before) with all of this fancy do-dad's in it. This rig even has OnStar in it if I want to prescribe to it. I got this vehicle from a police auction sale for a song and a dance.
The computer is telling me that the following needs to be serviced:
stabilitrak (I have no clue as to what that is)/
the airbag (why does the airbag need servicing)/
traction control (I have some idea on that, but I am not sure).
It drives like a dream. The vehicle is very responsive. I have to be really on top of my game when driving the vehicle. It takes a very tinny move of the wheel to change lanes. I am used to older cars that are not as responsive. Right now the computer says that the all wheel drive is off. I do not need the all wheel drive right now. But how do I turn on the all wheel drive for when I need it?