If you browse the list of issues, start with the first skinning tutorials, as they start at the beginning. But, you'll want to jump forward since DNN5 is a bit different than older versions.
I'd recommend that you look at these:
But that you then look at these:
After that, you should be able to go back and look at the others and, at the same time, be able to figure out what no longer applies. The tutorials that focus on pure CSS skins and the ascx approach to skinning will likely prove more useful.