Well, that's why I'm inclined to call in Cirno. Because unlike humans, Fairies don't stay dead.
And plus, we can talk her out of getting a cut of the cash by convincing her that it's the heroic thing to do, with the comment that we aren't a hero, just a mouse looking to get things done.
As for weaponry, I'd say get a hold of a Kusari-gama if possible, like Sour said, as well as wire for our Kunai, and something long, like a spear or pitchfork.