It's not hard compared to a front or rear bumper
There are lots of videos on youtube with
how to's. And if you buy the right film (with air channels) than its not that hard. With the air channels the film is actualy paper. Peels of realy easy but when its applied with presure it stays on. And with the air channels you have very little chance of getting air bubbles underneath because it can escape true the channels. If you do the spoiler, do it in 2 pieces. The upperside and underside. Otherwise you overstretch the film and it won't stick properly. When everything is applied heat all the film to 100 degrees so it stays in the shape of the spoiler and roof. Thats it realy.