Needs Improvement
Tutorials are useful in general, but there's a lot of badly formatted spaghetti code in what you submitted - especially in what you call the GTA, [asteroids style] clip movement. That code is horrible, and could be rewritten with far fewer lines. You also initialize a bunch of variables you don't even use, which suggests to me that the code has been adapted from something else.
If you have access to Flash MX or MX2004, I suggest you create a key listener object instead of using the key.isDown approach - listeners are more responsive.
You might like to take the sample code and place it in a text area to make it more viewable.
You can also get much better performance with custom cursors by using an onMouseMove handler with updateAfterEvent();, and simply set the x and y coordinates of your clip to the _root._xmouse and _root._ymouse values every time the event handler fires. The drag method was used back with Flash 4, but you'll notice that it does nasty stuff when you try to use it while handling a draggable movie clip....
Hope this is of some help.