Of course you will be lost.
That skin use the old version of Rainlendar (or Rainlendar 0.22.1).
To convert to the new format check this post: www.rainlendar.net/cms/index.php?option=com_kunena&Itemid=42&func=view&catid=9&id=13427
You will need to install Python.
Or here you have the converted version. (inside the zip file there is a .r2skin)
(Maybe you don't know but you can use all the windows from that skin but use the tooltip from Shadow4. Click on Advanced>>> in the Options/Skins tab. The open the left tree, select the tooltip from Shadow4 and then click on the Right arrow)