vector graphics

I just looked again and I see you have arrow shapes, so perhaps the lines would better suit use of a library movie clip symbol also... with the registration point at the base of the arrow. You could calculate the length and the angle of rotation based on the differences between the x and y coordinates between the points.
Others may have other ideas for how to do this.

I would be inclined to do this with an array of point objects:

http://livedocs.adobe.com/flash/9.0/main/00002050.html#wp428765

take a look at the Point object methods...e.g. offset

And use the drawing API commands

http://livedocs.adobe.com/flash/9.0/main/00001933.html#wp386253

You can draw each segment with a lineTo for the next Points x and y properties.

You also need to place movieclip dots (using attachMovie) for each visual representation of a point and to permit the mouse events and startDrag activity for moving them etc.

That's a very quick idea of how I would do it, perhaps I would change things were I actually doing it.

This is not a super complicated project, and you say you are new to flash 8, but you don't say if you are new to flash. If you are also new to flash there's a lot there to get familiar with in one go. If that is the case you probably want to run through some of the examples for each aspect of what you need to do. Start with the examples in the help files... look for online tutorials if you need more understanding.