I don't raise my 300CD up at all to drain the oil. There's a "low spot" in my driveway that gives me enough clearance to unscrew the plug and drain the oil out.

If you want the extreme solution you can buy an "oil vacuum" that will remove the oil through the filler. I'd only recommend this if you feel as though you absolutely positively must spend the $80 or whatever it is for the vacuum.

Does some oil remain in the motor regardless of how you drain it? Sure it does, but as long as you change it hot and change it often, no reason to get paranoid over it.