I want to try my hand at some different skins for the Droid X, but I don't know where to start. Are there any guides out there or would anyone be able to point me in the right direction?

From what I can tell from opening the zip file for a few different skins, there is a bunch of different .xml files and .png files. I'm guessing that I would just overwrite these .png files with mine and call it a day.

Also, my friend is interested in the theme, but he has a HTC Eris. How difficult would it be to port this over to his phone? I plan on making this from a skin for Liberty at first but was wondering if each ROM differs so that I'd have to make a different zip file for each one?