That is way to much to pay to change an oil pan gasket. And never take your car to a place like PepBoys or Wal-Mart. I don't know about Sears. I would find a reputable independent garage to first determine if your oil pan is leaking (cause it sounds like the dealership is trying to scam you). If it is leaking ask the independent shop how much they would charge.
Find a good garage here:
http://www.cartalk.com/content/mechx/find.html
Find a good garage here:
http://www.cartalk.com/content/mechx/find.html