Two questions. First is the an OBD reset tool that is recommended for my 05 3.2 A6 primarily for reseting my service light after oil change. Also my airbag light came on about a week ago and I was hoping there is a OBD tool that could diagnose or reset.

airbag light on? does your passenger airbag on or off? There are 3 things may occurs which i know of:
1. passenger sensor broken - with this, your passenger airbag will be off all time regardless whether there is passenger seating next to you or not. My car gets this.
2. your rear center belt tensioner is broken, another very expensive fix.
3. software glitch - can be fixed by updating some software.