You have to update your links manually. As long as the threads haven’t been purged due to old age or irrelevance (the threads you listed all still exist) you can find them easily with the search tool. Speaking of which, it’s such an improvement. The old vBulletin search tool was completely useless, this one here actually works 
edit (because Discourse complained about me trying to triple post 
):
For example the posts in this topic (had it bookmarked for years 
) look pretty broken, those [li], [ol] and [ul] tags don’t work anymore.
Is it possible to resolve this automatically with a software solution or is it something that has to be done manually? Then it’s probably a better idea to create new guides from scratch, especially in cases like this when the info is years old and might not be accurate anymore.