According to the wording, Guidance is not a card with Overload. It overloads one mana, but it shouldn't count for the elemental.
This logic has already been shown to be inconsistent with other mechanics. For example Rocket Backpacks and Special Delivery. Literally every first minion you play gets a copy summoned, even though it's not technically a "Rush minion," as stated on the card. I know there was at least one similar example in constructed play as well but just can't recall it at the moment.