Looking to Buy a Used D6N 2005 ish 10,000 hrs Any thoughts?

Hello,
I am in the market for a Used Dozer and Ive been looking at the used CAT D6N LGP 2005-2008 with anywhere from 5,000 - 13,000 hrs on them.

I dont want to buy a headache

Any thoughts? what should I look for? What kind of major repairs should I brace myself for with a machine of this age?

opinons greatly apreciated!