Finally getting a camper!

You probably won't need one. Hook it up and see how much rise you get on the front wheels that would indicate the front is being unloaded by the tongue weight. My guess is that you won't see much. I'm running in the neighborhood of 425lbs with my truck and have very little change when I am towing.

If you really wanted to quantify it, hook up and go weigh where you can weight each axle. Get a weight with the camper attached and then without. The difference on the front axle weight is how much the tongue weight is unloading the front.