Hi Steve,
My wife and I and our 2 daughters live in Missoula. Your son will do well, especially if he's willing to take a lesser job than his dream job at first.
I loaded my pickup and drove to Boulder, CO from PA in 1992. I stayed one night in a motel and signed a lease on an apartment the next day. Worked picking up scrap from trimmers and framers for a month till I found full time temp work and then a permanent job in CAD drafting and design. My future wife came out to CO a month after I did and also worked temp jobs for a month or so till she found a position. We were both college grads but took what was available.
Subscribing to a couple local papers in different areas for a few months before making the move helps give you an idea of what the communities are like, jobs, real estate, etc..
Contact me here if he needs a hand. Don't worry too much Dad, he'll love it!
Tim