You don't say how heavy the boat is and how steep/slippery the ramps are.
Of course you need to learn to back the trailer. Assuming you know how to do that, it doesn't matter if it's 20ft or 2000ft backing up.
My only aversion to dunking the host with the camper on is if it was a steep/slippery or soft ground at the launch. A lot of weight on the rear w the camper plus the boat pulling it backwards combined with unloading the front wheels some if you're on an incline, @ss downhill, could make for interesting getting stopped or pulling back out.
BUT you have a diesel so you'll pretty much always have good weight on the front and 4wd. So put er in 4 lo then you can creep down in reverse and less chance of stalling coming out. AND you have a manual trans, so don't trust the e brake to hold the whole mess from rolling back into the water when you get out to unhook the boat!
Don't want to see you in the "boat ramp bloopers" thread on another forum I frequent!
Better yet, leave someone in the drivers seat at all times with that heavy rig until safely off the launch ramp.
I'm pretty paranoid of that after seeing trucks floating around the launch! Especially with a stick shift and an e brake that is sketchy holding 18klbs on a slope. If I'm unloading the boat then I'll wait in the cab until wife/buddy etc comes around and takes over in the truck.