These guys are out near Herkimer:
Don Brown Bus Sales - School Bus Inventory
I bought my bus from them, and they delivered it. Before it left, they threw in a new starter and a full tank of diesel. I was able to work with a sales guy there who actually went out to the bus and got me info by climbing under it. They also did the initial inspection right there too.
From what I can tell, they seem a bit more pricey than Craigslist or some of the auctions (and the wonderful finds I hear -other- people getting), but I was able to lock in a manual transmission (which was important for me), and they have plenty of the T444E & the DT466E engines in there just now ...