If you backed Journeyman, you could get free replacements for Item 1/2 and Quest 1.
This is basically all the info you need:
https://boardgamegeek.com/geeklist/198820/im-new-myth-what-do-i-need-update
What I have done:
*Replaced the core 5 heroes with 2.0 cards. Keep the 3 exclusive heroes as-is for now. The cards still work.
*Ditch all items, including expansions. Start fresh with 2.0 items. You can get replacement expansions via the
KS for free.
*Ditch all the quests, including expansions. Start fresh with 2.0 items. You can get replacement expansions via the
KS for free.
*Any monsters you get a new card for, replace it. The old monster cards are still valid, just a clearer format. Grubbers/Crawlers/Shamblers have been released, the other 3 will come with Journeyman.
*Darkness and merchants are unchanged.
The only cards which MUST go are quests and traps. Everything else is just restructuring of the same content and the 1.0 stuff is usable with the 2.0 rules.