a) If you win a raffle, they should issue you a 1099-G. You can offset that gambling win, if you can show gambling losses. Which is one reason to have a member's card if you hit the casino frequently. They can print out your gambling history and show what you won/lost over the year. And Yes, we have a few people that hit the casino's fairly frequently and come in with 8-10 1099-G's showing their winnings. They also have a printout showing what they spent/lost that year.
b) The FFL can't "give" or "sell" you the prize for a lesser amount. The organization holding the raffle sets the value/price. And even if you turn around and sell them for less then the value, you still won a prize worth the original amount, and will be taxed on that amount. However, since you have sold the prize, you will now have money to pay the taxes...