What would be the best process to update a Gallery that's been tweaked in Lightroom.
By far the easiest thing to do would be to trash the existing page and import the new version of the gallery making sure that the Nav Order for the new Gallery Page is the same as the old Gallery Page (so that it displays in the same menu order).
What would happen if instead of re-import.... through FTP I replaced the contents of the Juicebox gallery. Would that screw up Showkase's database?
I would not recommend this at all. You would have to upload the gallery folder to somewhere on your web server anyway and the importing process does not take long so I would certainly just upload the gallery folder to your 'temp' directory and allow Showkase to import the gallery correctly.
But when I try to name it "landscapes", suddenly it reverts to having only 7 images, which was the state of the old landscapes folder that existed before the new import.
Changing a page name should not have any effect on the images or configuration options listed in a gallery's XML file. It sounds like there may be some server-side caching going on which is causing your problems. (When you revert to an older page name which previously existed, the corresponding older version of your gallery's XML file seems to be used. If you have since modified the gallery, then it sounds like the data must be coming from a cached version somewhere.)
If your web server is caching files, try switching it off to see if this helps.
So if I had previously created a folder with the name "landscapes", trash it, and then later create another one with that name, the characteristics of the previous folder may get put onto the new one.
I cannot replicate this behavior. I created a new Juicebox gallery page, named 'landscape', with a couple of images and a couple of custom settings. The gallery displayed as expected. I then trashed the page and the 'landscape' folder was moved to the '_trash' folder. (The 'landscape' folder no longer existed in the Showkase root directory.)
Next, I created another new Juicebox gallery page, again named 'landscape' with two different images and all default settings. Again, the gallery displayed as expected. Only the two new images were displayed and none of the original gallery's custom settings were used. A new 'landscape' folder was created in the root Showkase directory using none of the original 'landscape' folder's data.
I suspect that what you are seeing is due to some kind of caching (whether server-side or in your browser) so please check into this to see if it might be the cause of your problems.