If you want to disable the front airbag so as to put the child in the front DONT.
I have seen too many fatal accidents where the car seat has been in the front. The little nippers get more protection in the back and if their in the front you eyes will be looking at them and not the road.
I agree with Marcos - my daughter went in the front and my wife spent more time wiping her chin than driving - gave me heart failure!
When I tried to do this on both the C and the ML I was told no - not only does the airbag require disabling but some cars have the explosive tensioners on the front seatbelts.....
My son has never been in the front, and after 7 months he's not suffered!