Is applying a ceramic coating difficult?
Applying a ceramic coating is easy. It's all the other stuff that's hard.
Getting the paintwork polished to a satisfactory standard takes skill and experience. Ensuring that it's done right requires you to check and check again under the right lighting conditions. Once the sealant goes on, you will seal in the paintwork, whatever the condition of the paintwork. If you left swirl marks or buffer trails, you'll be stuck with them.
Once the paintwork is properly prepared, you put on the ceramic coating, and then you take it off again, this is actually far easier than applying some waxes. Really easy.
However, timing is essential. There is a window of time you have to work within, with thin margins of error, and if you go outside that margin, things can go badly wrong. If you leave it on too long you'll be in trouble, take it off too soon, it will be a mess. Humidity, moisture, heat, cold, air movement can all greatly affect the window you have to operate in. Applying ceramic coatings in a clean, controlled environment is essential, because if your coating isn't curing evenly, it's impossible to take it off evenly.