DNN skinning has not changed greatly in years - so what it relevant for 5.x is pretty much 100% relevant for 7.x.

The thing to understand is that there are actually two different types of skins - being skins based on HTML and skins based on ASCX markup.
HTML skins use TOKENS - while ASCX markup use skin object markup directly.

If you create a HTML based skin - what actually happens is that when you import the skin into DNN - it is internally converted to ASCX markup.
FWIW - we find that its much easier during development to use ASCX - as you can make changes inside the portal on the fly and see the effect of the changes immediately.
If you go down the HTML path - you need to edit the HTML - package up the skin - and re-import it every time you make a change to the HTML.

The only area that is not well documented currently are some changes to the markup of the different skin objects - which alter there functional in minor ways - most often these are related to turning on legacy flags to prevent things new social elements such as message notifications being shown on user controls.

Westa