Being new to the diesel scene would you be able to tell if the turbo or FICM was new?
Does he have the documentation to support all this repair work and why was it done? I would want real good answers to those questions. I would also want an oaisis report on it to see if there have been any real serious problems with it in the past.
Find a good diesel mechanic who knows what to look for in a 6.0 and have him look it over first.
It's a lot of money for the miles IMO, but if it is clean and been taken care of it is worth it.
One more thing to remember though....the motor is not the only thing with 250,000 on it either.