Try getting in touch with Zimex Aviation in Zurich as they operate quite a few aeroplanes which are based there. There will (should) be someone who can put in contact with the right people and individuals. Are you operating on behalf of a client company? If so their local manager or base commander (or similar title) should be able to go and find these things out for you, and help you with the necessary arrangements.
I operated out of there for a few years, but almost 10 years ago now. It's not as bad as everyone says. They are a bit laid back, but friendly and helpful as long as you aren't too pushy. You have to do it all at Sahara pace!