I wish I had a folder of all the base images used in a basic skin. Then I could just replace the images...
If you use the diamond WB you can save all those images to start with. If you use the same image sizes you won't have to mess around with settings and paint margins.
There are many images you can make different sizes but doing that requires one to make painting adjustments and other adjustments at times. Best to make a basic WB. That will help you to feel your way around SS somewhat. Than if you want to make images different sizes for certain graphics you will have a better feel for messing around with margins and such. Sometimes its best to mess around to see what changes when you change things. You aren't going to learn what SS can do till you have made several skins and spent a lot of time.
We all welcome new skinners and look forward to you progress. If you have specific question make a thread people will be glad to help when you run into problems.