1997 F350 Powerstroke sputters off idle

[Infinite Monkeys]

Hi,
This is my first post here.
I'm looking into buying a brand new (for me) 1997 F350 with 225000 miles on it. The current owner tells me that it starts and idles fine, but sputters under power. I have not looked at it yet, but would love to have a few suggestions to keep in mind when I'm checking it out. I plan to change the fuel and fuel filter when I see it to see if that helps. I will also get a compression test done at the dealer before buying it. I'm pretty handy with gas motors, but no experience with diesels.
It is an manual tranny and the previous owner bought it with a cracked bell housing. He replaced it and put in a new clutch and flywheel. He also does not have any experience with diesels. I do trust what he is telling me (up to a point).
The truck has been sitting for about 2 years and he says the problem suddenly arose and then he parked it. So new fuel may not fix it, but can't hurt.
Thank you for your help.