Greetings!
As Jack said, intonation is really a pain in the neck, especially if you want to play with others. Genereally you can alter every note's pitch by applying more or less of pressure on the reed, so you'll always sound more or less in tune by yourself, but with accompaniment, it does not work anymore.
Thankfully I was able to get mine with a ghamish (reed) made for it. There are a few possibilites on where to get one, yet I personally would stay away from the ebay ones (and ebay in general)
I got mine, which I like very much, from a store called "Gandharva Loka", went to Graz and tested it (unfortunately, the Graz-shop has been closed, but there are a few others around central Europe and one in Berlin)
Another option would be, to go to Armenia or other regions where it is played and contact a local duduk maker, or maybe, if you're lucky, send a friend who know the language xD
If you can try it out or have somebody experienced play it for you, you'd know what you're getting in to.
Now, I don't know what kind of woodwinds you play, but compared with my kaval and all of my woodwhistles as well as traverse flutes, the duduk provides more backpreassure (far more than pennywhistles). So it feels kind of different at first.
As for the fingering, I only play by ear. Have not figured out what scale it is xD Unless you are used to cover the holes with the tip of your fingers (like classical flute players would do with the mechanics) it should not be much of a big deal.
To me, ornamentations came quite quickly; vibrato is performed with the lips altering pressure on the reed, glissandi and trills come naturally from the fingers.
The hardes thing to learn would be the circular breathing, still have not maneged that....
If you have specific questions, I'd gladly try to answer them, yet I am not a professional at all....
btw. there was a instructional video by Gevorg Dabaghian on youtube somewhere, I'll try to find it, it might help you a bit
---Edit----
Found the video, here is the link to part 1. Make sure, that annotations/subtitles are on, because he speaks Armenian here. Hope it helps
http://www.youtube.com/watch?v=bYoDSVvSTCI