It does use some concepts from Lost Legion, but as far as I know they are adequately described in the Tezla rules.
The one issue that comes to mind is that the new hero will have two unique cards in his starting deck instead of one, as that is one of the Lost Legion changes. You could optionally replace one card with a basic card from another hero to give him an equivalent starting strength.
Pretty much this. Though I'd actually suggest searching for the new hero deck cards online. Once you get the wording, I'd just find a way to mark the corresponding 'standard' card in the hero deck.