Did I do something stupid?

You didnt get a good deal, I don't think you got screwed either. I would grab an rc monster motor mount and battery tray asap than a 9xl motor with rc monster heatsink clamp. I would also grab a mamba monster the second mike gets them in (which should be very soon) also toss that motor and control back on feebay straight away! O yea I forgot get a polyquest 4s 5000mah pack from mike.