I agree with Roger & Mary, the Progessive devices come with a lifetime warranty too. And they're made in the US, not China like the Surge Guard brand. Might cost a bit more, but their warranty is legend. eBay or Amazon for the standard prices. Craigslist if you're looking to save even more.
If you tend to travel from a good park (resort type) to a good park, you won't really need an EMS for a while. If you tend to stay in remote parks with poor infrastructure, then get one soon.
Many RV parks in the US now have pretty good Wifi. But I use a high gain antenna on a 30 foot USB cable to take advantage. Wifi boosters generally need to integrate with the parks modem so they aren't much use as parks don't like you plugging into their modem. Wifi extenders work well if you can find a place to put it and power it where it sits between the parks antenna and your RV.