A easy measure that would help for future:
Gamepress to put a date of change on every piece of text.
Another continous 2-step-measure that would help:
(1) Mark every piece of text, all Guides and other Informations given, that is older than one month as "possibly outdated".
(2) Reread every piece of text that is "possibly outdated" mark them as "valid" or "outdated"