02 F250 7.3 4x4 purchase help

[TLaiche]

I am looking at buying a diesel and I came across a 2002 F250 7.3 4x4 for a good deal.
The only thing I'm concerned about is that it has 249k miles.
I don't know much about diesels so I need a little help.

Is 249k too many miles?
What should I look for when looking at the truck?
How much life could I expect with routine maintenance?

Any help is greatly appreciated!

Thanks!
Taylor