2004 f350

I am looking at a 2004 F350 with a 6.0 diesel with 68000 miles and priced at 19000. I have heard that the 6 liters are problem packed. I used to work with a company with two F550s with them. One has had the fuel injectors replaced and the head gasket, and the other has had a few minor problems. I know another guy with the same exact setup as the company I worked for and he has never had a problem with it. I am going to be using it for regular driving and pulling trailers at times. Any advice would be greatly appericated. Thanks.