the above is a map of what to put in .
You need to keep your a head unit or a BMW head unit if you want
to be able to repair your car or get warranty work done on it as
the BMW repair computers won't talk to the car without a BMW head unit in it. This apply s to the 2011 especially as you still have warranty on it.
Some people sell there stuff on ebay.
You might even get a bite here for the Hi Fi stuff.