I think the Topkicks and 4500's start with a 6.6 Duramax and go bigger from there. I have never owned a Duramax, but I am looking ay maybe a newer or 1-2 year old 6.6 with the allison transmission.

So my question is, for someone whom has never owned a Diesel, what do I need to know? and if I am looking at 1-2 year old ones, when I am checking them out, what should I look for to know I am not being taken by a shady deal?