There are a few tutorials, but there isn’t a UI available for managing iocage jails until 11.2 is released. If you’re not 100% confident in setting it up and diagnosing any problems entirely via the command line it’s probably better to just wait for that. There will be an official MineOS plugin for iocage in 11.2, so you can get around to upgrading then. (Also, if it’s working for you, why spend the time fixing something that isn’t broken?)
If you have the files mounted outside the jail, upgrading will be even easier. Just re-mount the dataset back into the same place in the new jail and you’ll pick up right where you left off.
You should be able to import just the necessary server files via the webUI. When looking at the server status, there will be an option to select the server’s profile, i.e. the server software/version being used. Select the appropriate profile and hit the “copy to live server files” button. This should insert the .jar and relevant files into the directory.