Some of the earlier DPF/DEF emissions systems were known to be problematic on Dodge, Ford and GM diesel trucks, do some searching on that particular year. Things like frequent regens, poor fuel economy, DEF sensor issues come to mind. I am always leery of buying a used vehicle from a car dealer selling a different brand, makes me think the PO got disgusted with his truck and traded it for a different brand. A Ford dealer may not know or may not care to know, about issues with another brand. I have always bought used vehicles from private parties and never had any problems.
2004.5 GMC SLT CCLB, Ride Rites, Turbo brake, EFI Live
2012 Arctic Fox 29 5T 5th Airborne, B&W, Prodigy
Papillon navigators Lily, Buddy and Willow