Rules and Errata

FAQ:
Do I have to wait until after my first scenario before I can replace a boon with the Core or Curse version?
No, you can replace cards from your Class Deck box with the Core or Curse versions before playing your first scenario, or after any scenario.

Resolution: On page 8 of the Guide, for the last bullet point of Modifying your Class Deck, replace "If your Class Deck box contains boons that have the same name as boons in the Core Set or the Curse of the Crimson Throne Adventure Path, in between scenarios, you may replace these boons with the Core or Curse versions." with ""If your Class Deck box contains boons that have the same name as boons in the Core Set or the Curse of the Crimson Throne Adventure Path, before or after a scenario, you may replace these boons with the Core or Curse versions."

History:
"If your Class Deck box contains boons that have the same name as boons in the Core Set or the Curse of the Crimson Throne Adventure Path, in between scenarios, you may replace these boons with the Core or Curse versions. (Card names must match exactly, though differences in spacing such as Short Sword and Shortsword are allowed.) Do not take cards from the vault for this—you must bring your own copies. If the level of the Core or Curse card is higher than your tier, you can’t replace that card until you’re allowed to put cards of that level into your deck."

Given that many players mistakenly think they can't change their decks before the first scenario, since it says 'in between', I suggest changing Vic's text to:
"If your Class Deck box contains boons that have the same name as boons in the Core Set or the Curse of the Crimson Throne Adventure Path, before or after a scenario , you may replace these boons with the Core or Curse versions. (Card names must match exactly, though differences in spacing such as Short Sword and Shortsword are allowed.) Do not take cards from the vault for this—you must bring your own copies. If the level of the Core or Curse card is higher than your tier, you can’t replace that card until you’re allowed to put cards of that level into your deck."

Keith Richmond:
"Before or after scenario makes sense.

In the case of something like changing a Level 0 Crow for a Level 1 Crow, that's fine as long as your character is Tier 1.

Anecdotally: At one point I'd hoped we could remove the +X, so that a Returning Throwing Axe could replace a Returning Throwing Axe +1, but that was more complex than people wanted."