In the camper, yes. In the *back* of the camper- not necessarily. You're going to need to be aware of your tongue weight - too light and you can induce sway; too heavy and it can put you over your rear axle weights. Generally speaking, with travel trailers, you want approximately 10-15% of the trailer's weight as tongue weight.
When you weigh, *each*-time, you want to do 3-weightings:
1) trailer and truck with WDH engaged
2) trailer and truck without spring bars for WDH (throw the bars in the bed of the truck)
3) take the camper and park it, put the bars into the camper and go weigh the truck by itself
(I wrote an article on How to Weigh a Travel Trailer
that explains in a little more detail about these 3 weightings.)
You want to make sure nothing changes between each weighing, otherwise it can skew your math. People in the same seats, load in the same places, etc.
With CAT scales, you pay $10 for the first weighing and then $1-2 for each subsequent weigh within 24 hours.
You'll need a few weightings to get your WDH dialed in. The dealer isn't going to do it right, sadly. They just don't know enough about your loads, where it's going, etc to do it properly. So plan on learning its instruction manual and redoing that.
You will see how moving things or adding/removing water makes a difference. Many people will even buy a Sureline scale so they can measure tongue weight at home (knowing their basic camper weight from prior weightings).