You started the engine without a prop? Never do that. The engine will easily over rev and destroy itself.
It's pretty much standard procedure to replumb the tank on an older plane. For that matter, I do it every other year on my planes.
As for the tail fin, is it the whole vertical stabilizer? That's usually a broken glue joint or actual broken wood. You'll need to see the break to decide the best method of fixing it. That might mean taking covering off. Working epoxy completely into the joint and then making sure it's all pressed tightly together while it cures should fix it.