So. I need to replace a battery on mine, but are there any precautions I need to be aware of before I do so?

Ive read that the satnav needs to be idle before swapping a battery.. How do I go about doing this without knackering the Mk4 BMW satnav system thats in the boot?

When people talk of the Satnav unit, are there referencing the drive thats sticking out of the carpet on the right hand side into the engine bay, or are they talking about another control unit under the boot carpet near the battery?

many thanks chaps.