Can anyone tell me how to make it so that when I am inside a trigger area, an action will allow me to build an M1A1, and then it will pop up at a marker?
Use a repeating trigger:
type anyone
condition:player in thislist (only player will activate trigger this way)
on activation: build=player addaction ["Build Tank","buildtank.sqs"]
on deactivation: player removeaction build
Of course, "buildtank.sqs" would be whatever script you choose.
The build action will be removed when you leave the trigger area, or you could remove in the script.
To build the tank, your script would have something like this in it (in case you don't know already):
tank="m1a1" createvehicle getmarkerpos "markername"