Just purchased a 2018 Express SWB passenger van. While it has the "humps" in the headliner for AC vents there are no vents. Wondering how much trouble it is installing vents for the rear passengers?

 

Quite a bit of trouble. You'd have to buy a dozen or so pieces of OEM ducting which won't be cheap. You would also need the rear heater core, rear A/C evaporator, blower motor + housing. Then you would have to install the T fittings in the front for coolant and refrigerant and run plumbing for both to the rear of the vehicle. The plumbing is woven throughout the body and frame, possibly even before the two are married togeither. Wiring for the motor, mode selector switch and temperature control. You're talking about a few thousand dollars just in parts and god knows how many hours of labour. Not worth it in my opinion.

 

I think that depends on how much you like your rear-passengers.