Possible..yes. cheap, doubtful. The end result will look as good as the amount of destruction and reconstruction. These things are built in an order, with a roof going on last. This implies that removal of the roof is the only way to get it looking factory.
I would suggest watching some YouTube videos of how they are assembled. Would be nice if you can find one for your model, but really anything of similar construction will help you understand.
I am starting the process of converting a 45 ft horse trailer into a unit that has living quarters. Using these videos has given me plenty of ideas.