have seen a lot of posts on this subject, but not answering this very simple possible solution:

I would like to replace my L322 BM54 with a BMW BM54 which has aux enabled. and then connect a aux bluetooth adapter to the BM54 in the trunk, thereby creating a bluetooth connection for me to run streaming music(spotify) over car speakers.

here's my questions:
1. Can I buy: http://www.ebay.com/itm/12V-Bluetooth-modu...2335017090 and then just cut the cable and plug directly into pins 3,4,10 on the upgraded BM54?
2. Can I use the 12v from the 12V ANT OUT on the BM54? or anywhere else on the pins?
3. where can I connect the 12V negative? thought about running it over to the 12v connection on the other side of the trunk, but rather long and should be somewhere nearer to connect this? just to a ground somewhere?

all responses appreciated!

The eBay item would fit in place of the CD changer,

This would fit in armrest transmit Spotify to your factory radio on an fm frequency