Be sure and size the brakes for the weight of the camper. I have a 1,500lb dry camper with a 2,000 lb axle. It takes 7" brakes. A 3,500 lb axle will take 10" brakes.
I installed mine myself. It was easy as the backing plate was already there. One thing I found was that the oil seal couldn't be mounted flush with the outside of the brake drum, but must be recessed 1/4 of an inch (closer to the bearing) to ride on the smooth, raised part of the axle shaft. The first one I left flush and damaged the seal. Your experience may be different, but it's worth a checking if you are doing the job yourself. Don't forget the trailer break-away switch, (and a battery source if your camper does not have a battery) which is a legal requirement in most states if you have brakes.
Chip