Hey there. I have to say wow 550000 miles. That is alot. I guess the way i would have to say do you think the truck is worth some more miles? Have you taken it on the road and test drove it? If so. Does it handle well? Also if your gonna spend the money on the truck. I would suggest to take it to a dealer and spend some extra money to look it over. Give it a good fine tooth coming put it on the lift and just go all over it like there is a special prize hidden and try to find it. For 7 grand i would say that is a good deal just as long as the engine and trans are fine i would pay that for it. Good luck on the truck and 550000 miles is a rechord to me for a powerstroke i havent heard of any over that. I know of a cummins that has over a million it is a 95 model. The guy is waiting for a few to catch up so they can have a million mile club. Take care and hope the truck works out for you.