How hard is it to replace a airbag?

I found a good deal on a 2007 ford focus which has a blown airbag due to a little damage to the front bumper the damage is minor and i would be able to buff it out my self. The big issue is that there is a blown airbag on the steering wheel. Is it as simple as taking the old airbag out and plugging a new one in? or is there a lot more to it.