If I were to own an ATV I would probably just repair it myself. I would not want to spend money on paying someone else to do it. Is it hard to learn do it yourself ATV repair?
I think it depends on whether you have any mechanic skills and how exactly is the ATV broken. A lot of people know how to fix minor issues by checking a Factory Service Manual to walk you through the basic problem, but for complicated repair work, I think the professionals know best...
Its got an engine which is just like any other engine. If you are mechanically inclined its easy, if you are a white collar, paper pusher then you'll have issues.
Do your research, then dive in. It's fun and not nearly as hard as you may exspect. But remember to do your homework and research any procedures, a "little" knowledge is dangerous. If not sure of something...ask! Also important, use the proper tools.
If you really think you can do it, and want to spend the time on it, then go for it. You can try to research the problem, and if it looks like something you can fix and feel up to the challenge, then by all means, do it.