Anyone tried/know how to do this?

I do not think it is possible.

it would be cool. But I doubt its possible....

I am pretty it is not possible. It has been out for over a year now, you'd think if it was... someone would have done it by now.

I've seen some recolors over at Aqua-soft.org Other than that. no reall "skins" per se.

Not exactly a skin for iTunes but it may satisfy your needs:
http://www.ipodsoft.com/softwaredetail.aspx?sid=10

Yeah, someone's working on it. Development is a little stalled at the moment.

You could try this dude - Clicky

It skins iTunes for Windows into a more funky Mac style. Very, very good stuff.

Hope it helped.

That could be really cool, though iTunes doesn't look bad as it is