Thanks for the response, everyone! I'll be sure to let our DM know about the sword and the monster rules.
As for how we did in the fight: I stormed in with my Avenger before we realized these weren't the pushovers we'd been facing, but the Helmed Horror and Mad Wraiths ended up rolling pretty...
It's the third session of the D&D 4e campaign I'm in, run by one of the players from our previous 3.5e campaign, and we're still trying to get the hang of it - especially the DM, who was upset about my Passive Perception being "so high you find everything" (except for traps), which led to my...