Congratulations for the new camper!
The Fastguns are very convenient . You don't "need" them, but if you have used them once, you probably "want" them.
I would test drive the setup before adding any modifications. Orherwise, it will be difficult to pinpoint any handling issues and decide what is the most effective way to take care of them.
Whether the trailer fits behind your truck without some sort of hitch extension, I don't know. Surely someone who actually pulls a trailer will chime in. The same goes for the generator question.
Do yourself a favor and weigh your rig when you are done. Get the individual axle weights. You will then know how close to the axle ratings of the truck you really are.
