1. Yes, it is. I do that all the time. Like u said, use setpos and getpos code.
2. The "detected" trigger works like this:
You make a trigger covering whatever radius u want,
Choose West, East Res, Civ, or if u want the condition to be a guy or vehicle, us the group option and drag the line from the unit to the trigger. This will make the unit available in the trigger.
then set activation to "detected by west/east"
Then under effects, sounds put play alarm.
U can add a patrolling group of guys or something that will come runnning to the trigger this way:
Make the guys, then give them a waypoint like Seek and Destroy into the trigger area.
Syncronize the starting waypoint of the guys with the trigger. Then when it is activated, they will come running after you.
3. This, for some reason, I don't now (although I should...)
P.S. The AK 47 will forever be better than the AK 74
Hope this helps