This link has some good info to explain how payload capacity works.
Take a look at this label for you truck and post back.

Also, there are other factors that determine the overall pulling weight.
Dodge has a neat site to look up your truck. Put in the truck type, cab type, rear end, 4wd, etc..
http://www.ramtrucks.com/en/towing_guide/Another thing, check the rating on your receiver. (Typically there is a label on it)
Congrats on wanting to get a camper. We bought our first one last year and the research process was "fun" :E. But after you figure it out, you will understand and be happy that you got something that goes together.