Sorry if this has been asked before, I was searching and couldn't find anything.

My friend and I are trying to learn the game and he had a card with 1 health and he had repair droid out. If I do 1 damage to that other card can he stop it with repair droid or is that only good on vehicles that take more than 1 damage? Thanks.

The simple answer is no. The effect on the Repair Droid is an action, and as such cannot interrupt or react to the damage being dealt. The damage "resolves" before the droid can be used.

Ok, thanks. That's what I thought but we weren't sure.