What do you know that can go wrong with a 2008 ML320 CDI?

My mom is about to buy one, and I am looking for Oppos advice about any know issues on this model. The car only has 12,000 miles on it, so it is barely broken in. A friend that only used it while she vacationed in the USA three months a year is selling the vacation pad and staying in the UK full time. But my mom wanted me to check for any issues before she gets out of a warrantied Genesis and into an out of warranty Merc which would have expensive repair bills (if it ever needs something). What say you Oppo?

(ps, NPOCP at $24,000?)