OH wait, it's April 3rd. Well, you know what they say...
In all seriousness, this would probably void a good amount of your warranty, and iDrive glitches won't be covered either. You already ask a bunch of serious technical questions that nobody has necessarily come across since it will end up being much more than the $2100 that the iDrive option costs, to retrofit. As you said, $700 for just the dash, that's 1/3 the iDrive cost from the factory!
335xi sedan 6MT, Premium, Cold Weather, iDrive, CA, iPod
Black Sapphire Metallic, Black Leather, Aluminum Trim
European Delivery: April 28 - May 7, 2008
Performance Center Redelivery: July 11, 2008