I did it on a previous TT. I contacted the manufacturer (Starcraft) and told them what I wanted to do. They were quite helpfull in providing a drawing showed stud / rafter locations. They had no drawings showing any electrical in the ceiling.
I used a spiral cut zip saw, with blade depth set to cut only the thin ceiling material. After prying out the ceiling cutout, I did find some 12 volt lighting wires that needed to be moved. Then I used a long drill bit to drill up through the roof in the four corners. Last, up on the roof, connect the four holes and cut out the roof hole.
Installing the vent, I made sure to use a lot of caulking, in addition to the putty that comes in the install kit. I was pretty nervous about cutting a hole in a brand new trailer, but, all worked out well.