Most hitches I see for the frontier are class 3.So correct me if I'm wrong , to pull the pop up camper I need the class 4 hitch receiver and wiring harness installed ? Is that it
Also beware that there are 2 types of " plug and play wringing harnesses. You might be tempted into getting this one which simply taps into the brake and turn signals. Don't get it. Due to the increased load of the trailer turn signals, the flashers will not flash properly or at all due to the thermal/mechanical/electrical flasher relay. Same principle as LED turn signals but opposite.
2006 Nissan Frontier Custom Fit Vehicle Wiring - Hopkins
Instead you need the more complicated harness that has the relays in it. This is the factory method of adding trailer wiring
2006 Nissan Frontier Custom Fit Vehicle Wiring - Tekonsha