Create a better one, and then ask a moderator with jurisdiction over that board to switch the pinned thread. There's no need for any big debate about it: if there's a thread which hasn't been updated in several years, and somebody is asking me to pin a different thread which seems better after a few minutes of skimming, I'm probably just going to do it. (But please try asking other mods first, rather than me.) If somebody ends up having a problem with something-or-other regarding the new thread, then
they can make a better thread, and we can
at that time have a public debate in Meta about which up-to-date thread is better.
2. Let Mods edit out the outdated information?
Mods are not supposed to edit the
content of a post, even if it's a sticky. Mod edits should be limited to non-content things like fixing broken bbcode, merging posts, etc., so that nobody ever has reason to complain that a mod "put words in their mouth". Even if a post is violating the rules, and editing out a word/sentence/paragraph would make it no longer in violation of the rules, this kind of content-edit should not be done; the post should just be deleted.