With an older RV do yourself a favor & spend the bucks for a good surge protector and lock box.Buy the biggest and best that you can find..
You should be able to get a good 30 amp one for $260 to $350 @ Camping World.
It could save you from replacing all the electronics including the microwave,TV's and shore to coach switch-over powerbox in your coach...
All it takes is a bad pedestal power box combined with a power spike or excess low/high voltage (don't ask how I know this)