I want a Unimog now

After attending the WA GTG, and seeing the 2 Unimogs that showed up, I want a Unimog now. I am wanting to find out a little more about them, and was wondering if anyone can tell me the difference between the models, and what years are the best. What engines are the best on milage, I am guessing it would be a diesel. I am also wondering if I can buy a drivable one in the $4,000-$6,000 price range. Thanks in Advance for the help, since this will aid me in my researching of Unimogs