I haven't ever used a chicken vet. Partly because we can't afford it, and partly because the closest one is
waaayy far away. I've only really needed one once though, when we were dealing with what we
think was mareks.I don't know a whole lot about chicken diseases either, just enough. I wuold recommend getting a copy of the chicken health handbook. It was written by Gail damerow, who is a chicken expert, and she is
amazing! She has also written the Chicken Encyclopedia, which is probably my favorite book that she has written.
If you ever have a chicken who dies of either extremly bad sickness (i.e., not moving at all, sick for days, etc.) or if other birds are acting like the sickie did before they died, then I would get a professional autopsy done. It is a great help in determining what exactly happened to your bird and whether or not it is contagious. Here is a link that list the state vet labs - all of them:
http://www.the-chicken-chick.com/2015/06/chicken-health-poultry-management.html If you ever have any questions about your flock, look it up on this website. The Chicken Chick is the next best thing to Gail herself
If you ever have a chicken with a serious injury though, I suspect that any
good vet would do their best to help them.