Hi Bert, first off we need to be careful about Artisteer versions, and "Artisteer 3x" is not precise enough. mojoPortal 126.96.36.199. is set up to work with Artisteer 3.0 only, so if you're using RC1 or a prior beta, you should upgrade. One other red flag I see is that you should not need to do step #4. If you overlay your Artisteer export on top of the Artisteer30-verticalmenu1 files from the 188.8.131.52 version of mojoPortal (found in /Data/skins/Artisteer30-verticalmenu1), then those changes will already be in place and won't need to be added manually. The "important skin updates" are strictly for people who need to update their already existing skins when upgrading to a new version.
Other than that, in general it sounds like what you are doing is right. The only piece I haven't personally tried is deploying a skin via zip file like you have done. If you have access to the server, you should make sure that the directory /Data/Sites/[site number]/skins/[your skin] exists, and has all of the appropriate files in it.
About the tutorial, there is a document about creating a skin from Artisteer 3, but I suspect you have already looked at that.