Marvin,
If you are not planning on moving the trailer and basically are using it as a "guest cottage", you may not need a surge suppressor. Do you have a whole house system on your home's main entry service? Some places require that as part of the residential building code, and it's always optional.
The main reason people use surge suppressors and EMS systems on RV's is because the varying quality of electrical service at RV parks can very often be iffy, wired wrong, under voltage, over voltage, etc.... and any of those can smoke your electrical components in the trailer. At your home on known good power it 1) may not be necessary in the first place, and 2) if your home has a central or whole house surge suppression system, would be redundant.
The other thing to consider is if you don't have a whole house system, it's not much more to install one (it takes a licensed electrician as they have to wire in into the main entry panel and the power has to be cut at the street by the power company). It will then protect not only your "guest cottage" trailer, but all the appliances and other stuff in your home.
But again, at home on known good power, you may not ever need it (but I would put in the 30 amp RV style outlet so you can properly power the trailer in the heat of summer with the AC on. They could put one in along with the whole house protection suppressor, or that part can be a DIY if you are comfortable working on AC voltage circuits)