Our 5er is set up for a 2nd AC unit up front including a 50 amp service and dedicated 20 circuit with 12 ga wire in the ceiling near the front ceiling vent. I'm thinking about installing the 2nd unit ...
A lot depends on how your rig is set up but you can usually either hook it to the ductwork, or use an air distribution box with either mechanical controls or wall mount electronic. Many rigs use a multizone thermostat, with control lines run to the front vent, or you can install a separate thermostat.