Almost anything can be repaired,
and almost anyone can repair it.
The question is how good of a repair do you want?
A repair can be as minimal as tape, glue or nail it together or fill the ding with putty and put some color on it or use a felt tip pen to color that scratch and call it good. Or, one can use any and all tools, material and talent necessary for a near perfect repair. Of course, the first option is going to be the least expensive, you can do that yourself. The second option, will, of course, be the most expensive. However, many times there can be an acceptable solution somewhere in the middle.
You ask what I consider a near perfect repair and what is in the middle that is acceptable. Well, I consider a near perfect repair one that would be acceptable for display in a museum. Because I worked for several years on museum pieces and because many repairs will naturally lend themselves to a repair of that quality, I always try to get there even if we are going for the something in the middle.
The something in the middle is a repair that is — when you stand three feet away from it and you didn’t know it was there you probably won’t see it; if you knew it was there you may see a hint of it.