How do I open the key to replace the battery.

Thanks in advance

I found this guide useful: http://www.riskin.org/vwkey/

It's then not too difficult to do, once you've done it a couple of times.

Put the key in a warm place to make the plastic case soft.

Flip open the key and at the "join line" under where the key blade is parked, there is a slot. Put a screwdriver in the slot and turn it gently and the two halves of the case will separate. The battery is a CR 2032.

rotodiesel.