I did this to my boxster I know how you feel. In the boxster one is blue the other is black and at 6am they looked the same. I poured a pint of water into the engine oil wondering why the water level was not moving
Anyway I digress. Don't start the engine. I called the AA and they came round laughter at me and then set about fixing it at my house. They literally siphoned it all out and then put in new oil. Took about an hour.
I ordered myself up a dunce hat and I suggest you do the same. Bad luck buddy.
E90 330i SE Auto Graphite Grey Metalic