JohnInKansas has given a wealth of very good info and advice. I'll just add some things from my own experience.

I am first and foremost a fiddler/violinist. I inherited a beautiful bowl back mandolin from my grandmother, who had brought it with her when she moved here from the Old Country. It was fun and easy to play because it is tuned and figured just like the violin. The strings are harder on your fingers than violin strings, but you'll build up the necessary calluses in time. Playing mandolin was very valuable to me as a fiddler because it taught me to "think" in chords or at least in double stops. JohnInKansas has given a good explanation of the demise of my mandolin. He said In the usual construction the inside of the bowl was lined with linen cloth, and the bugs seem to like it when they're left in the attic for a few years. One day I opened up my mando case and found hundreds of little pieces of wood. The mandolin had shuttered so badly that it couldn't even be glued together. I cried a lot. I suppose the bugs had eaten the cloth and the glue that held all the pieces of wood together.

A few years later I bought an entry level mandolin from a local store. When I decided that I wanted to upgrade, I started going to used instrument shows with a friend who was as crazy as I. These shows are so much fun. There are wondrous stringed instruments on display tables (no cases) tables, and you can pick up and try anything you want. It's better than being a kid in a candy store. My friend and I both liked playing the mandolins, and our favorite ones were usually $800-$900 or something unthinkably expensive. We agreed with each other that Gibsons are the best and that you can tell a Gibson if you're playing blindfolded. Gibsons are just so easy to play. You get a good sound from them almost without trying. (The same is true of violins. I got a fantastic deal on one of those, too, but that's another story.) I eventually bought a used Gibson model A about 40 years old for $500. That is a very good price for a Gibson. My Gibson is not a great Gibson, but it is a Gibson. The model A ones tend to cost less than the model F ones because the latter are favored by bluegrass players. I think the sound of the model A's is a bit more violinistic. They sing sweetly. In fact, for years I went around looking for mandolins and telling people that I wanted one that sounded like a Carolina wren.

My mandolin now needs repairs. I asked on a Mudcat thread for a good luthier in the Wash DC metro area. Several people recommended Jim Bumgardner, and they all said that he might be retired. I called him, and I got the impression that he only takes jobs that appeal to him, and mine didn't. Any more recommendations? HMT recommends Steve Carmody, but I've heard mixed reports about him. I'd appreciate some more advice.