I personally draw blood to test for Johne's since I also test for CAE and CL at the same time. The only trouble I have with drawing blood is when my Guernsey doe decides that she doesn't have veins! I have been searching around and it looks as though the only place in Idaho, from the same state as you, that does Johne's testing is Sage Ag Labs, located in Sweet. They only do blood tests but run them on Thursdays and send reports on Fridays. Here's their link: https://www.sageaglab.com/content/goat-johnes-testing
I would say that milk test would probably be easiest but did some research and cannot find a place in Idaho that does milk testing. Also did some research on the fecal testing and they say that is the most accurate since they look for the genetic material, but again, cannot find a place that does it. Hope this helps!