As mentioned a bit of overkill on the truck but better too much than too little.
We have done similar (see signature).
If you are good on a 30' boat, a 30' 5th wheel will seem downright spacious...especially since there is no need to launch the dingy just to take a walk.
Your budget will get you a nice setup though a 2015 truck will eat up the bulk of it. We just picked up a 2009 34' 5th wheel last year in very nice condition. The prior 28' unit was only $4500 and was pretty much trouble free for a decade of use.
Big thing to make sure of is no water damage. Everything else is pretty reliable and/or easy to fix.