You shouldn't need to uninstall JFBConnect before re-installing/upgrading it. However, it shouldn't hurt to do so. When you do uninstall, all the files should be deleted. The database tables will be left intact though, so you won't loose your configuration settings.
Folder::create: Could not create directory Path: /home/chxogjob
Warning: Failed to move file! (The chxogjob referenced is a name from an old host.)
If you're seeing a path from your old server, it means that you likely haven't updated your configuration.php file with the proper tmp path on the new server. It could be some other cached value. There's nothing in JFBConnect that stores the directory path, so if you're seeing that warning, it's a Joomla configuration error.
I hope that helps get you going, but if not, let me know.
Thanks,
Alex