Beginning DotNetNuke Skinning and Design has shipped, but it's woefully out of date, being published almost a month ago. :)
You might look at DNNCreative.com, the new stuff is up to date. It's a worthwhile subscription for skinning, and many other DNN functions. The lastes two issues have especially good current videos. I regretfully have to recommend staying away from Skincovered, since Nina's departure from the core group there's been a marked drop in new materials. But the older stuff is still valid for the most part. One good resource is the default skins that shipped and installed with DNN. They use current tags, such as [NAV] instead of [MENU]. And when you get stuck, ask for help here.
Jeff