Expanding on Daniel's reply, you
can use Inventor files from other sources. Besides being cool to look at, it is just plain smart to use the resources you have at your disposal.
Just watch out for correctness - some parts may not be the same as in this year's kit, like the window motors.
It is a very good idea to make sure you give credit where it's due and absolutely never take credit for someone else's work (GP). Speaking of really cool Inventor stuff, check out
Charles Bliss' Inventor Site where there's a wealth of downloadable parts (though some are in Inventor v9 now).