I've researched this topic and thought after many unsuccessful attempts, I'd hopefully be able to help someone else out there wondering what shark fin can be used, how to remove it, how to replace it, and what the process looks like in a simple DIY.
The damaged fin has a scratch and is the one with the black residue not the lighter gray residue.
Unfortunately, uploading the pictures was an issue, but at least I can explain the process and you can reference them if necessary.
1.) Find a replacement fin - I'm not sure if I can identify where I got the fin from, but just check an online junk yard for high class vehicles (...new was ~$150 from bmw, I paid $50 for a 2011 oem). All e9x series fins are the EXACT same and regardless of what options you have/want i.e. bluetooth, sirius, etc the housing still is a constant.
2.) Removing broken/original fin - grab some fishing wire and just separate the fin from the roof. It's very simple, there's no chance of damaging anything, you're simply breaking a seal of 3m automotive tape between fin and roof.
3.) Cleaning old residue off roof - I used alcohol and little diluted goof off. The clear coat is pretty resilient, especially on the roof so don't be afraid to opt for the diluted goof off. I didn't use straight goof off, as I didn't want to test the limits on the clear coat of a $5000 roof. Also, a blow dryer can help in the process. I live in the Boston, so the weather does not cooperate when removing any type of adhesive.
5.) Apply extra strength 3m tape (you can get it at lowe's, home deport, autozone) to all contact areas of new fin. I poked the 3 positioning points through paper, drew the margins, and then placed parchment paper over the paper so I could place the 3m tape over the margins and cut with a razor blade in order to prep the 3m tape. Whether or not you want to use this method is up to you. I found it to be very easy and user friendly.
6.) apply fin to roof with pressure for 30 seconds...and the rest is history.
7.) Will report back if any issues, but things look great, there's no gaps in 3m tape (i would assume this is important even though the housing is protected with a rubber washer and is encased in plastic).
Hope this helps someone out, enjoy.
Also, if you want the internal wiring portion with connection ports I have an extra. Not sure if this is useful for retrofits, but thought I'd throw it out there.
Last edited by mikefromMA; 03-10-2013 at 08:03 PM.