Okay, I've moved only the PhotoPost data into its new, separate database, copied my entire PhotoPost folder from the old site to the new, successfully installed PhotoPost, and incorporated headers that are the equivalents to the mock headers created for the PhotoPost demo. All is working great so far, with only a couple more items to resolve.
1. I need to run the userfix script Chuck spoke of above to "sync" up the PhotoPost IDs with the XenForo ones. I have found a lot of scripts on this site to do this for other integrations, but none for vBulletin 3.8 to XenForo. Does one exist somewhere, or can you please point to something that will achieve this?
2. Possibly related to #1: My logging into to PhotoPost does not seem to log me into XenForo, and vice versa.
3. I don't want Unregistered Users/Guests to be able to view even the index of my galleries, and certainly not the galleries themselves. This was working with the VB
integration, where you had to long in on the Photos home page to see anything. Now, I can see EVERYTHING without logging in, even though I have checked appropriate permissions on some of the categories. (These were apparently altered to match XenForo usergroups, but did not "line up" entirely accurately in terms of what was checked vs. what wasn't.
4. All cell padding is gone when viewing the PhotoPost pages in IE8 (the only browser I have to test). I read something about that being a problem with IE9 that was "easy to fix", but I can't find anything more about it. Please help.
Thanks again for the wonderful support!