To do the oil pan is not a difficult task if you have the time and handy with tools. Since this is not your transmission pan that is cracked, the engine oil is relatively cheap compared to the transmission oil. I am assuming that it's the lower pan that is cracked and if that is the case you could do it or find a reasonable indy shop. All the parts should run you arond the price as indicated by Mulchman but the labor should run you cheaper than what the dealer is charging. Personally I believe a job like this should run you about $500.
2008 650 Convertible- 6 Speed manual- Sport package- HUD- Lane Departure- Comfort Access- Merino Leather- HD Radio- SAT