The Fantastic Fan doesn't have to replace the passive vent that's at the rear of the trailer. A number of folks have put the power vent closer to the front... like across from the door. It will require a new hole in the roof. The benefit is "cross ventilation." You leave the passive vent open and the power vent blowing out... and it draws cool air into the trailer across the rear bed/dinette... unless it's hot out!
. That's my plan... the benefit is you get cool air without a fan blowing on you.
If you want an electric tongue jack.... a plate will (probably) need to be welded on the tongue with appropriate holes and the manufacturers jack removed.