Welcome to the world of archery. And as for your last question, your Bass Pro shop has the average price of most broadheads. The only place you can probably get them cheaper is on Ebay.
For your light draw weight I would recommend you stay away from mechanical broadheads and get a 'cut on contact' fixed blade. A few good ones are Slick Trick Razortrick or Viper Trick, Muzzy Phanthom, Steelforce, Magnus Stinger.