>If one paints a vanagon starter motor pink (required content!), they've
>"changed it", but not "changed it out".

You've changed its color or finish, not the motor itself.

>If one were to re-install it
>backwards, is it also changed but not changed out???

Changed its orientation.

>If one takes the starter motor out and replaces it with another one, it has
>been "changed out".  Right???

Wrong. You've changed it FOR ANOTHER. "Out" is utterly superfluous.

>Why then, when we replace a child's soiled diaper with a new clean one, do
>we say we, "changed the diaper" and not "changed out the diaper"???

Because the diaper's not out. The only thing that is out is the
diaper's contents...

If you remove an item and replace it with another, you've REPLACED it.

You MIGHT say, if someone's just bought your Vanagon and you've
emptied out your wallet changing the buyer's $100 bill, that you've
changed-out your wallet.
--
Andrew Grebneff
165 Evans St, Dunedin 9001, New Zealand
<andrew.grebneff@stonebow.otago.ac.nz>
Seashell, Macintosh, VW/Toyota van nut