Ok well this one is not too hard
For units you want to stay
alive, in a script put, unitname setcaptive true
this will make sure the enemy don't shoot at them. You could
also have some enemy unit to fire at cars or such, for
combat ambeience! For the second part, in a script put;
unitname setbehaviour"blue" I think thats the right one?
This will stop them from firing.