Rummage around the Colnago info sites and figure out the correct color/paint name and number. It is one the second owner now so "NOS" is not a good term to use. Colnago owners, in my opinion, are a little like Porsche owners in that some run them hard since that's what they are made for, some are fanatical perfectionists about them and will scream bloody murder if they find a speck of moth poop that you didn't disclose to them, and a lot are just average Joes who just like them and always wanted to have one at least once in their life (I've got my Colnago MasterLight, haven't swung getting a Porsche yet).
For high end bikes there is a guy at a local shop here that many people have run their nicer bike sales for them. He does nice pics, great words, and knows the shipping and auction game and also knows how to deal with the scammers.
With or without the components is up to you, but taking them off will leave the assembly marks showing and will possibly leave chipped paint behind in the clamped areas. 9 speed is closer to the 8 speed stuff on mine so for your's I'd probably sell it intact.
And have an honest story ready as to why you haven't put any miles on it. Nobody's business, but it is a curiosity. and I probably wouldn't mention the attic dust. In fact give the bike a good cleaning, there should be no dust on the bike.
As to price, put it up for what you need to get, the market will do the rest. Seasonal timing is important, depending upon your location.
Hope this helps some.