Need Buying Advice For A 2000 Ford F-350 7.3

Hey so I have a 2000 ford f350 with 350k miles I was offered for a old bmw i don't use. I was very interested because I need a truck and would love a turbo diesel but now here's the problems. So when I got there I wanted to scan vehicle ,the obd 2 port received no power and I seen some rewired wires in the cab. The truck takes a lil while to start about 10 cranks or so but it is cold and it won't rev over 2k rpm.The kid just bought it that I'm getting it from so I'm pretty sure he bought it and couldn't figure it out . So moral of the story is I'm very mechanically inclined and want the truck and believe I can get it running right but do these problems sound like the car is a lemon and should i save myself the hassle or can I bring her back to life I just care about the engine