1) Standard artillery scripts work by the being given an area to bombard, and then creating tank shells over the area in a random pattern. Download one and read the intstructions that should come with it.
2) RAR files are just one of many types of compressing files so that they are smaller. WIth teh correct software you can decompress them and take a look at whats inside.
WinZip will make .zip files, another form of compression, and probably the most common.
WinRAR will make .rar and .zip and about a billion other, my personal favorite and just as easy to use as WinZip.
3) Without knowing what addon you are using, then you'll find help few and far between.
4) Because a plane on teh taxiway or runway will takeoff automatically when a mission starts. The intro, is the mission.
5) A man jumping out of a chopper or plane should automatically get given a parachute. But just incase, create an Empty parachute and give it a name eg "PChute" then in the init field of your man put;
This MoveINnDriver PChute
The man will move to the same position as you placed the parachute and will wear it. You will see no visual indication of this.