The first year we rented a seasonal site, we asked some of our fellow campers the same question, for #1. Only one other seasonal camper was using surge protection and that was because they had been using the 5th wheel full time before settling down in the seasonal site. We did not bother with it. Our campground is very well maintained and where we are the sites are newer than the rest of the campground. If we were in one of the older sections, we'd probably have surge protection.
#2, using PVC instead of the stinky slinky is definitely the way to go if you plan to leave the RV there long term. Our site could get windy and before we switched, the stinky slinky would sometimes get pushed off it's stand and I always worried about the lawn guys hitting it with the string trimmer and putting a hole in it.
I would talk to your neighbors about #3 as well. The water at our seasonal site is well water. The wells are tested monthly. About 1/3 of the campers don't use any water filter, most use the Camco blue inline filter and that's also what we use. We use 2 through the course of the 5 month season - a new one when we got there and then a new one sometime around late June, usually around the start of summer.
-Michael
