First advice you need to know is know your weight ratings for a bumper tow and there might be a different one for a 5th wheel. Lastly you'll need to know the actual weight of your truck so that you can try and stay within the weight limits.
Then you'll need to know weight adds up because you'll have gear, hitches, and other hardware to worry about.
There's a lot to learn at first, but after you know it will make lots of sense. DON'T buy any trailer until you KNOW how this works. Salesmen are NOT your friends. They'll be glad to say whatever they need to say to make the sale. After that, it's your problem!