Hi
Basically, what do you need to change?
Colors and images, right?
Colors are set on template.css, style1-2-3.css, vm.css, k2.css and gk_stuff.css files.
Images can be changed by working with PhotoShop on source files.
How? Naturally, you need to have some knowledge on handling photoshop and after the changes done, you need to export the psd file with "save as web" option. It will generate a html file and images directory.
Check the images available on template directory and replace the ones generated by the psd file with the same name and format.
That's it!