Ok this is how I would like to see upgrades happen from now on and will post on the main site as well..
1) Make Back of DB and change the name of the forum folder to something like forum_backup take special note of any modifications they had before
2) copy ALL new files including the ones in the post http://www.fusionbb.com/forum/showtopic....
to the new site under the old forum directory since that way any remenants will not be there
3) copy the old forums config directory into the new forums config directory
4) copy the old forums language files into the new forums /language/XXX directory
5) take one of the new skins doesn't matter which copy it to a new skin call it yoursite and beyond compare that skin to the one they used prior for any differences and update the new skin with the old skins VALUES so they will be in the new skins format.. then copy that new skin into the new forums skin directory
change file permissions to 666 and directories to 777
7) perform update
redo any modifications that need to be done (some wont since they are now features)
if done this way then at the end you should have an old forum you can go back to..