To change a unit's appearance (besides its team color) you need to import and overwrite the texture that it uses. The texture is like an image that wraps around the model that would be blank without it. People call this art "Skinning".
I don't know skinning but if you want something so easily done you can try asking if anyone will create a black/white/pink haired version of your unit here:
http://www.wc3c.net/forumdisplay.php?f=178
But to be honest I really recommend just looking for a cool skin if you want something custom. Try here:
http://www.wc3c.net/resources.php?f=642
Or here:
http://www.hiveworkshop.com/forums/skins.php
The constructing animation is part of the model's birth animation, so - sadly - yes it would. ;-)I don't want to import.
How about a building's construction art? I added a new undead unit building but i cant find a way to give it the undead construction animation... Would this recquire importing as well?