8.5 quarts of Mobil 1 0W/40 synthetic and here are two DIY directions for changing oil.

http://www.slk32.com/pages/oilchange/oilchange.html

http://www.dfwsbr.com/crossfire/faq/oil/

The first set of instructions is a MB SLK 320 but everything applies to the Crossfire, as it is the same engine. They use a topsider to suck the oil out through the dipstick on the SLK instructons. You can also go in from underneath and remove the shield that covers the bottom of the engine to get at the drain plug as in the second set of instructions.