I had a 2000 Excursion and a 2000 E350, both with the 7.3. It's a great engine. One vulnerability, which has already been noted, is the Cam Position Sensor (CPS) that is mounted on the front passenger side of the engine. Usually when these fail, the engine will usually start and run for about 5 seconds and then shut down. I also had problems with the wiring harness that connected to the CPS and this could be causing an intermittent problem. I also had issues with the Excursion with the wiring harness to the injectors under the rocker cover rubbing and shorting out.
You might be time and money ahead to have a qualified diesel mechanic check it out and make any repairs. It's a good truck and would be worth the investment.
Bill J., Lexington, KY