First, download this:
http://www.megaupload.com/?d=RBHZ5329
then unzip it where ever you like.
next go into 'Skin Tool' and start replacing the files in the 'default' folder.
when you are done with that, open "makeskin_default.bat" and it will compress/compile your files into a .skn file
NOTE: Make sure to save any bitmaps in OS/2 24bit format. if you don't, the program will fail.
next place the default.skn (you can rename it if you want) file anywhere on your micro sd card, except in any hidden folders.
then boot up sakura and browse to the file and open it.
TA-DA! New Skin!