With the release of Winamp5 getting ever so much closer, I'll be going through nsdn and making a new section for it as well as adding as many docs as I can. As far as skinning goes, there have been updates to the winamp2 skin format to allow skinning of a few extra things.
If you have a tutorial or a faq in the works, please help me help you write it! or something... Or just submit it
th4nx d00dz, u p33pz r0x0r. awwww yeah.