Yes I have installed sunroofs, but never in a Dakota. I would not get a used one, it would very likely have a very bad leak problem. Best bet is to find a truck accesooies shop or independent car audio/accessories store that would have a better price, or maybe just have it installed. If you have the roof console with the computer and all that, a sunroof won't be compatible. If you don't have the console, you will still have to either relocate or lose the dome light.
"As long as you're in motion, you're moving in the right direction." - Ronnie Montrose