First off, just simply call Xbox. 1-800-4MY-XBOX. That way, you will be able to explain the situation and you if you do have to send it in, then you get a free repair, just tell them about 5 minutes later that your console has RROD. Next, if they whine about the tamper stickers or whatever, just...
I would attempt to play the game on both his and your system. If you think it has too much damage, try haggling the price. The Xbox has a very good disc drive, and can read heavily scratched discs with minimal problems, they also scratch fixer at blockbuster and walmart.