I am curious about your experience with US musician's unions. I think I'd like to take advantage of some of the union's benefits, but have some questions about how it works.

First of all I travel quite a bit, so would be playing outside my 'local' probably more often then not. Can I just join a National local (is there such a thing). Secondly, what are the restrictions? What do I have to tell them about my work? Thirdly - the benefits. I am most interested in buying insurance for my gear; instruments and sound equip. I presume I can buy good coverage for a reasonable cost. Yes?