scared of changing blog skin

I thought that changing a blog skin would be as simple.
Guess what it is not as simple as u think .
Just now I tried doing it guess what all my post was deleted u know how terrified I was.
So have a pro at your side or else.....
I tried uploading the blogskin of tsuna but guess what everything went wrong.
Why I want upload tsuna as my blogskin.
It will be in another post stay tune