I don't remember what year they started making them but the last year for hardbodies was 97.
I had a 97 se 4x2 automatic...that thing was slow as hell.
Gas mileage wasn't great. Usually around 24mpg.
I don't know what years you should avoid.
I didn't really have any issues with mine but I got rid of it when I got the rex. It only had around 65k on it. I do remember having an issue with the power locks but I got that fixed.
My quick search of autotrader leads me to believe that you'll get a fairly used and abused hardbody for 2k.
check the nissan forums, they usually have a section on the trucks http://forums.nicoclub.com/zeroforum/36