200,000 miles might not be excessive for that engine but keep in mind unless it was well maintained everything else on the truck may be in rough shape.

Also, just food for thought, but if the mileage is correct that means this truck was driven less than 10K miles per year. Diesels in general don?t like a lot of starts and stops and short trips where the engine doesn?t get up to operating temperature.

I?d be less worried about a five year old truck with that kind of mileage because at least you know most of it would be longer trips and highway miles.

Good luck.