Moving a modified theme to an upgraded version

[HCP]

I am using v1.3, and I plan to upgrade very soon. I just downloaded the latest version today. However, I have a modified skin from the Classic theme, and I saved the changes in a separate directory of my own. I do not want to have to reapply all the coding again, so I was wondering if I could just "paste" the modified directory into the upgraded version with the other themes? Was the themes directory modified in the upgrade? I just made template visual changes, not any complex scripts or anything like that.

[Nibbler]

There are theme update instructions provided in the docs.