We like the portable 30 amp Surge Guard. It not only protects against surges but also protects against high and low voltage. While you probably not need one for most campgrounds, if you do need one, the cost is significantly less than the cost of replacing much of the electronics in your Airstream.
As for the two 30 amp hookups on your Airstream, one is for the generator and one is for the campground hookup. This is assuming that you have a transfer switch in your Airstream, if not, they are connected together and there is not difference.