Yeah, you can only get guild leves for guilds in which you have membership, and you can only get them from the adventurers' guild in the city that houses the crafting guild (well, I'm pretty sure that there are some at camps too, but nuts to that). There isn't a way of checking in advance which leves will be repeatable, so you'll just have to try them out. It is always the same ones that are repeatable though, so once you figure it out, you're good.