Nobody enjoys the time lost, mess or work involved in a redecorating project.
Everyone knows experience is the best teacher. Yes, just about anyone can paint or hang wallpaper. The experienced professional, however, knows how to do it right, using the best materials and tools. Don't forget, when you redecorate, it will probably be for several years, and you will want it done properly. References, of course, will tell the story of past work and experience.