Hello Seraf,
I'm probably not the best one to help you with A.I, yet I can lead you into an excellent tutorial.
http://developer.thegamecreators.com/?f=t01/3d_tutorial_index
I have made a tutorial on Health boxes, that may be of some assistance to you.
http://curvedbasic.dbspot.com/DBTutorial.htm
Basically, you create a box on the screen, and when you get hit by the enemies bullet you'd subtract from your health variable.
For example, let's say the enemies bullet was a sphere with the object number 2 and you're object number 1.
If object collision(2,1)=1 then H=H-10
Combined with my above health box tutorial, this will subtract 10 from your health.
Then, you can simply have something like this to decide if you die.
If H<=10
print "Game Over"
end
endif
This will end your game.
Please post if further help is needed, and I'll try to assist you.
A book? I hate book. Book is stupid.