Whats wrong with my "02" 7.3

[gorrillaman]

I have just bought a used "02" f 350 with the 7.3 power stroke . I know I bought someones problem, but i want to make it a nice truck anyway. I think that I need a new turbo, I took it on a trip to Florida, I new that it was leaking oil, but I didnt know how much or even exactly where the oil was coming from. I put about 12 guarts in it in 2 days of travel. I also noticed that when I started pushing it with the load I was pulling it would get sluggish. I let out of it and accellerate again and it went back to top speed again. After a while when I pushed the accellerator I could here a squelling sound coming from the dash board on the drivers side. I got to Atlanta and she quit on me on the interstate, someone said replace the cps. I replaced the cam position sensor and eventually she started again. There was heavy traffic all the way to Florida so I could not open it up. She ran fine. As soon as I got out of the traffic and could, I started accellerating again. Up around 80mph. after a few minutes it started loosing speed. I could here the squelling noise againso I moved over to the side of the road and shut it off, it had been that a restart seemed to reset everything, This time it didnt restart and I had to tow it home . It still doesnt start but does turn over, What is the diagnois for the truck, and the potential cost to fix it.