I won't judge what you can or can't do but I will echo Mike in that any mistakes and your possibly buying a new roof.
There are you-tube videos on this and it *CAN* be done. The question is on your tolerance threshold for having to pay for mistakes.
As has been said there is a screw in the ceiling for a camper that is "AC ready" It is not in the center front to back, or side to side really.
That screw is an indicator on where to start. You have to make a square hole in the roof through all layers carefully and NOT sever the support beams or damage internal structure. Once you have safely made the hole you have to mount the roof unit and mount the inside air distro unit and controls. You will have to run wire conduit along the ceiling to the sidewall and possibly down the sidewall to a hole you poke in the side of the roof to expose a plug to the outside.
Finally, as described wire in to the power distro. box and put an outdoor plug end on it to plug in to the roof socket.
If that sounds like your cup of tea, here is something to watch: