you don't have to disconnect battery to do this mod, but consider that in case of any unexpected situation mostly connected with srs.

1. First of all you must disassembly your "central console" to get to the back of your main audio unit. It is not complicated and you need only screwdriver to do this, but in a few words: If you have 2010 G37 model:
- pry off little panel (plate) just bellow air condition buttons - now you will see screws
- remove the shift stick and then pull off panel and unplug all wires behind it - it will be easier when stick shift will be on N or D
- now remove all screws and remove panels (control panel and a/c and radio panel)
- no you can remove screws that holds main av unit

2. On the back of main av unit find the connector M206 (M82 symbol was used in older 2009 G37 manual, in newer wersion this connector is called M206)

3. Make new wires - you will need them to connect bluetooth receiving device. It is simple - two wires for each channel ending with the female cinch (I joind the L and R grounds)

4. Now you have two options:
- cut black, green, white and red wires in M206 connector and solder them to your new wires or
- don't cut the wires and just remove little of isolation from them and attach new wires

Here in Poland XM radio doesn't work - so I completely don't need it and I cut the wires. But choose option which you want :)

5. I bought bluetooth receiver device called Nokia MD-310. Why ? Because:
- I can connect multiple phones to it
- it has very good audio quality
- it is powered by old standard nokia car charger
- I had good price for it

6. I bought nokia car charger and disassembly it. I soldered power cables to the 12V socket in armrest

7. Connect your new audio wires to the bluetooth receiver.

8. Now put everything together. Pair your phone with bluetooth device, choose XM radio and voila !