I have a Progressive Industries unit that is similar to that one. I chose PI over Surge Guard because the PI unit is made in America, while the Surge Guard one isn't. PI also has a lifetime warranty.
As for putting in a GFI, if you have three-wire outlets already you can simply replace an existing one with a GFI one. If that is the first outlet on the circuit everything else on that circuit will also be protected. Many coaches use an outlet system that is a bit more complicated than typical household items, so you may need to go to an electrical supplier rather than Wal-Mart to get the proper item. As long as your exterior outlet(s), bathroom and kitchen outlets are GFI-protected you are safe.
This would be a good time to inspect all of your 120V wiring.
David Lininger, kb0zke
Heartland mpg 181 (sold)
1993 Foretravel U300 (for sale)