*~*~*~*Cakes' Closet*~*~*~* Come on in girls!
You could just install mario as is. But would be better if you put Rockin Rainbows on first. Then the mario add on for Rockin' Rainbows after that. There are actually to parts u need to install for UD 2.5.0 Rockin Rainbows because so much is themed. The instructions are right under the pics for that as well.
Hope that helps. If not shoot me or Cakes a pm. We will walk u through it.